diff --git a/crypto-primitives/Cargo.toml b/crypto-primitives/Cargo.toml
index ad74dcda..affa780d 100644
--- a/crypto-primitives/Cargo.toml
+++ b/crypto-primitives/Cargo.toml
@@ -26,6 +26,7 @@ ark-serialize = { version = "0.5.0-alpha", default-features = false, features =
 blake2 = { version = "0.10", default-features = false }
 sha2 = { version = "0.10", default-features = false }
 digest = { version = "0.10", default-features = false }
+merlin = { version = "3.0.0", default-features = false, optional = true }
 
 ark-r1cs-std = { version = "0.5.0-alpha", optional = true, default-features = false }
 ark-snark = { version = "0.5.0-alpha", default-features = false }
@@ -42,8 +43,8 @@ print-trace = [ "ark-std/print-trace" ]
 parallel = [ "std", "rayon", "ark-ec/parallel", "ark-std/parallel", "ark-ff/parallel" ]
 r1cs = [ "ark-r1cs-std", "tracing" ]
 crh = [ "sponge" ]
-sponge = []
-commitment = ["crh"]
+sponge = [ "merlin" ]
+commitment = [ "crh" ]
 merkle_tree = ["crh", "hashbrown"]
 encryption = []
 prf = []
diff --git a/crypto-primitives/src/commitment/blake2s/constraints.rs b/crypto-primitives/src/commitment/blake2s/constraints.rs
index 07f28ca8..3989d974 100644
--- a/crypto-primitives/src/commitment/blake2s/constraints.rs
+++ b/crypto-primitives/src/commitment/blake2s/constraints.rs
@@ -1,13 +1,11 @@
-use ark_relations::r1cs::{Namespace, SynthesisError};
-
 use crate::{
     commitment::{blake2s, CommitmentGadget},
     prf::blake2s::constraints::{evaluate_blake2s, OutputVar},
 };
 use ark_ff::{Field, PrimeField};
 use ark_r1cs_std::prelude::*;
-
-use core::borrow::Borrow;
+use ark_relations::r1cs::{Namespace, SynthesisError};
+use ark_std::borrow::Borrow;
 
 #[derive(Clone)]
 pub struct ParametersVar;
diff --git a/crypto-primitives/src/commitment/blake2s/mod.rs b/crypto-primitives/src/commitment/blake2s/mod.rs
index cab562ed..724f3771 100644
--- a/crypto-primitives/src/commitment/blake2s/mod.rs
+++ b/crypto-primitives/src/commitment/blake2s/mod.rs
@@ -1,5 +1,4 @@
-use super::CommitmentScheme;
-use crate::Error;
+use crate::{commitment::CommitmentScheme, Error};
 use ark_std::rand::Rng;
 use blake2::Blake2s256 as b2s;
 use digest::Digest;
diff --git a/crypto-primitives/src/commitment/constraints.rs b/crypto-primitives/src/commitment/constraints.rs
index 5124e5a5..e7a533ee 100644
--- a/crypto-primitives/src/commitment/constraints.rs
+++ b/crypto-primitives/src/commitment/constraints.rs
@@ -2,7 +2,7 @@ use crate::commitment::CommitmentScheme;
 use ark_ff::Field;
 use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::SynthesisError;
-use core::fmt::Debug;
+use ark_std::fmt::Debug;
 
 pub trait CommitmentGadget<C: CommitmentScheme, ConstraintF: Field> {
     type OutputVar: EqGadget<ConstraintF>
diff --git a/crypto-primitives/src/commitment/injective_map/constraints.rs b/crypto-primitives/src/commitment/injective_map/constraints.rs
index bc9dc628..13a9d67f 100644
--- a/crypto-primitives/src/commitment/injective_map/constraints.rs
+++ b/crypto-primitives/src/commitment/injective_map/constraints.rs
@@ -5,7 +5,6 @@ use crate::commitment::{
         Window,
     },
 };
-
 pub use crate::crh::injective_map::constraints::InjectiveMapGadget;
 use ark_ec::CurveGroup;
 use ark_ff::{Field, PrimeField};
@@ -14,7 +13,6 @@ use ark_r1cs_std::{
     uint8::UInt8,
 };
 use ark_relations::r1cs::SynthesisError;
-
 use ark_std::marker::PhantomData;
 
 type ConstraintF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
diff --git a/crypto-primitives/src/commitment/injective_map/mod.rs b/crypto-primitives/src/commitment/injective_map/mod.rs
index 700edf7b..ca32904c 100644
--- a/crypto-primitives/src/commitment/injective_map/mod.rs
+++ b/crypto-primitives/src/commitment/injective_map/mod.rs
@@ -1,10 +1,10 @@
-use crate::Error;
-use ark_std::marker::PhantomData;
-
-use super::{pedersen, CommitmentScheme};
 pub use crate::crh::injective_map::InjectiveMap;
+use crate::{
+    commitment::{pedersen, CommitmentScheme},
+    Error,
+};
 use ark_ec::CurveGroup;
-use ark_std::rand::Rng;
+use ark_std::{marker::PhantomData, rand::Rng};
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/commitment/mod.rs b/crypto-primitives/src/commitment/mod.rs
index 30edabeb..c94db15b 100644
--- a/crypto-primitives/src/commitment/mod.rs
+++ b/crypto-primitives/src/commitment/mod.rs
@@ -1,7 +1,7 @@
+use crate::Error;
 use ark_ff::UniformRand;
 use ark_serialize::CanonicalSerialize;
-use ark_std::rand::Rng;
-use ark_std::{fmt::Debug, hash::Hash};
+use ark_std::{fmt::Debug, hash::Hash, rand::Rng};
 
 pub mod blake2s;
 pub mod injective_map;
@@ -12,8 +12,6 @@ pub mod constraints;
 #[cfg(feature = "r1cs")]
 pub use constraints::*;
 
-use crate::Error;
-
 pub trait CommitmentScheme {
     type Output: CanonicalSerialize + Clone + Default + Eq + Hash + Debug;
     type Parameters: Clone;
diff --git a/crypto-primitives/src/commitment/pedersen/constraints.rs b/crypto-primitives/src/commitment/pedersen/constraints.rs
index 8386815d..8dec380a 100644
--- a/crypto-primitives/src/commitment/pedersen/constraints.rs
+++ b/crypto-primitives/src/commitment/pedersen/constraints.rs
@@ -7,11 +7,10 @@ use ark_ff::{
     fields::{Field, PrimeField},
     Zero,
 };
+use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::{Namespace, SynthesisError};
 use ark_serialize::CanonicalSerialize;
-
-use ark_r1cs_std::prelude::*;
-use core::{borrow::Borrow, iter, marker::PhantomData};
+use ark_std::{borrow::Borrow, iter, marker::PhantomData};
 
 type ConstraintF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
 
diff --git a/crypto-primitives/src/commitment/pedersen/mod.rs b/crypto-primitives/src/commitment/pedersen/mod.rs
index e1aa0d4b..96345322 100644
--- a/crypto-primitives/src/commitment/pedersen/mod.rs
+++ b/crypto-primitives/src/commitment/pedersen/mod.rs
@@ -1,17 +1,15 @@
-use crate::{crh::CRHScheme, Error};
+use super::CommitmentScheme;
+pub use crate::crh::pedersen::Window;
+use crate::{
+    crh::{pedersen, CRHScheme},
+    Error,
+};
 use ark_ec::CurveGroup;
 use ark_ff::{BitIteratorLE, Field, PrimeField, ToConstraintField};
 use ark_serialize::CanonicalSerialize;
-use ark_std::marker::PhantomData;
-use ark_std::rand::Rng;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
-use ark_std::UniformRand;
-
-use super::CommitmentScheme;
-
-use crate::crh::pedersen;
-pub use crate::crh::pedersen::Window;
+use ark_std::{marker::PhantomData, rand::Rng, UniformRand};
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/crh/bowe_hopwood/constraints.rs b/crypto-primitives/src/crh/bowe_hopwood/constraints.rs
index a9bf49de..fd0c433b 100644
--- a/crypto-primitives/src/crh/bowe_hopwood/constraints.rs
+++ b/crypto-primitives/src/crh/bowe_hopwood/constraints.rs
@@ -1,19 +1,18 @@
-use ark_ec::twisted_edwards::{Projective as TEProjective, TECurveConfig};
-use ark_ec::CurveConfig;
-use core::{borrow::Borrow, iter, marker::PhantomData};
-
 use crate::crh::{
-    bowe_hopwood::{Parameters, CHUNK_SIZE},
+    bowe_hopwood::{Parameters, TwoToOneCRH, CHUNK_SIZE, CRH},
     pedersen::{self, Window},
     CRHSchemeGadget, TwoToOneCRHSchemeGadget,
 };
+use ark_ec::{
+    twisted_edwards::{Projective as TEProjective, TECurveConfig},
+    CurveConfig,
+};
 use ark_ff::Field;
 use ark_r1cs_std::{groups::curves::twisted_edwards::AffineVar, prelude::*};
 use ark_relations::r1cs::{Namespace, SynthesisError};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
-
-use crate::crh::bowe_hopwood::{TwoToOneCRH, CRH};
+use ark_std::{borrow::Borrow, iter, marker::PhantomData};
 
 type ConstraintF<P> = <<P as CurveConfig>::BaseField as Field>::BasePrimeField;
 
diff --git a/crypto-primitives/src/crh/bowe_hopwood/mod.rs b/crypto-primitives/src/crh/bowe_hopwood/mod.rs
index d284c3ef..89a4ca27 100644
--- a/crypto-primitives/src/crh/bowe_hopwood/mod.rs
+++ b/crypto-primitives/src/crh/bowe_hopwood/mod.rs
@@ -2,28 +2,28 @@
 //! specific Twisted Edwards (TE) curves. See [Section 5.4.17 of the Zcash protocol specification](https://raw.githubusercontent.com/zcash/zips/master/protocol/protocol.pdf#concretepedersenhash) for a formal description of this hash function, specialized for the Jubjub curve.
 //! The implementation in this repository is generic across choice of TE curves.
 
-use crate::Error;
-use ark_std::rand::Rng;
-use ark_std::{
-    fmt::{Debug, Formatter, Result as FmtResult},
-    marker::PhantomData,
+use crate::{
+    crh::{pedersen, CRHScheme, TwoToOneCRHScheme},
+    Error,
 };
-#[cfg(feature = "parallel")]
-use rayon::prelude::*;
-
-use super::pedersen;
-use crate::crh::{CRHScheme, TwoToOneCRHScheme};
 use ark_ec::{
     twisted_edwards::Projective as TEProjective, twisted_edwards::TECurveConfig, AdditiveGroup,
     CurveGroup,
 };
 use ark_ff::fields::PrimeField;
 use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use ark_std::borrow::Borrow;
-use ark_std::cfg_chunks;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
-use ark_std::UniformRand;
+use ark_std::{
+    borrow::Borrow,
+    cfg_chunks,
+    fmt::{Debug, Formatter, Result as FmtResult},
+    marker::PhantomData,
+    rand::Rng,
+    UniformRand,
+};
+#[cfg(feature = "parallel")]
+use rayon::prelude::*;
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/crh/constraints.rs b/crypto-primitives/src/crh/constraints.rs
index 81c0aebd..28ea34b4 100644
--- a/crypto-primitives/src/crh/constraints.rs
+++ b/crypto-primitives/src/crh/constraints.rs
@@ -1,10 +1,8 @@
-use ark_ff::Field;
-use core::fmt::Debug;
-
 use crate::crh::{CRHScheme, TwoToOneCRHScheme};
-use ark_relations::r1cs::SynthesisError;
-
+use ark_ff::Field;
 use ark_r1cs_std::prelude::*;
+use ark_relations::r1cs::SynthesisError;
+use ark_std::fmt::Debug;
 
 pub trait CRHSchemeGadget<H: CRHScheme, ConstraintF: Field>: Sized {
     type InputVar: ?Sized;
diff --git a/crypto-primitives/src/crh/injective_map/constraints.rs b/crypto-primitives/src/crh/injective_map/constraints.rs
index 1a60c842..5d034c99 100644
--- a/crypto-primitives/src/crh/injective_map/constraints.rs
+++ b/crypto-primitives/src/crh/injective_map/constraints.rs
@@ -1,13 +1,11 @@
 use crate::crh::{
     constraints,
-    injective_map::{InjectiveMap, PedersenCRHCompressor, TECompressor},
+    injective_map::{
+        InjectiveMap, PedersenCRHCompressor, PedersenTwoToOneCRHCompressor, TECompressor,
+    },
     pedersen::{constraints as ped_constraints, Window},
-    TwoToOneCRHSchemeGadget,
+    CRHSchemeGadget, TwoToOneCRHSchemeGadget,
 };
-use ark_std::{fmt::Debug, marker::PhantomData};
-
-use crate::crh::injective_map::PedersenTwoToOneCRHCompressor;
-use crate::crh::CRHSchemeGadget;
 use ark_ec::{
     twisted_edwards::{Projective as TEProjective, TECurveConfig},
     CurveConfig, CurveGroup,
@@ -17,6 +15,7 @@ use ark_r1cs_std::{
     fields::fp::FpVar, groups::curves::twisted_edwards::AffineVar as TEVar, prelude::*,
 };
 use ark_relations::r1cs::SynthesisError;
+use ark_std::{fmt::Debug, marker::PhantomData};
 
 type ConstraintF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
 
diff --git a/crypto-primitives/src/crh/injective_map/mod.rs b/crypto-primitives/src/crh/injective_map/mod.rs
index 289a9006..f84ea1f8 100644
--- a/crypto-primitives/src/crh/injective_map/mod.rs
+++ b/crypto-primitives/src/crh/injective_map/mod.rs
@@ -1,16 +1,15 @@
-use crate::Error;
-use ark_std::rand::Rng;
-#[cfg(not(feature = "std"))]
-use ark_std::vec::Vec;
-use ark_std::{fmt::Debug, hash::Hash, marker::PhantomData};
-
-use super::{pedersen, CRHScheme, TwoToOneCRHScheme};
+use crate::{
+    crh::{pedersen, CRHScheme, TwoToOneCRHScheme},
+    Error,
+};
 use ark_ec::{
     twisted_edwards::{Affine as TEAffine, Projective as TEProjective, TECurveConfig},
     CurveConfig, CurveGroup,
 };
 use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use ark_std::borrow::Borrow;
+#[cfg(not(feature = "std"))]
+use ark_std::vec::Vec;
+use ark_std::{borrow::Borrow, fmt::Debug, hash::Hash, marker::PhantomData, rand::Rng};
 #[cfg(feature = "r1cs")]
 pub mod constraints;
 
diff --git a/crypto-primitives/src/crh/mod.rs b/crypto-primitives/src/crh/mod.rs
index 08cb4a6e..e0e214b7 100644
--- a/crypto-primitives/src/crh/mod.rs
+++ b/crypto-primitives/src/crh/mod.rs
@@ -1,20 +1,15 @@
 #![allow(clippy::upper_case_acronyms)]
+use crate::Error;
+use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
+use ark_std::{borrow::Borrow, fmt::Debug, hash::Hash, rand::Rng};
 
-use ark_std::hash::Hash;
-use ark_std::rand::Rng;
 pub mod bowe_hopwood;
+#[cfg(feature = "r1cs")]
+pub mod constraints;
 pub mod injective_map;
 pub mod pedersen;
 pub mod poseidon;
 pub mod sha256;
-
-use crate::Error;
-
-#[cfg(feature = "r1cs")]
-pub mod constraints;
-
-use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use ark_std::borrow::Borrow;
 #[cfg(feature = "r1cs")]
 pub use constraints::*;
 
@@ -22,13 +17,7 @@ pub use constraints::*;
 /// variable length CRH may also implement this trait in future.
 pub trait CRHScheme {
     type Input: ?Sized + Send;
-    type Output: Clone
-        + Eq
-        + core::fmt::Debug
-        + Hash
-        + Default
-        + CanonicalSerialize
-        + CanonicalDeserialize;
+    type Output: Clone + Eq + Debug + Hash + Default + CanonicalSerialize + CanonicalDeserialize;
     type Parameters: Clone + CanonicalSerialize + CanonicalDeserialize + Sync;
 
     fn setup<R: Rng>(r: &mut R) -> Result<Self::Parameters, Error>;
@@ -43,13 +32,7 @@ pub trait TwoToOneCRHScheme {
     /// Raw Input type of TwoToOneCRH
     type Input: ?Sized;
     /// Raw Output type of TwoToOneCRH
-    type Output: Clone
-        + Eq
-        + core::fmt::Debug
-        + Hash
-        + Default
-        + CanonicalSerialize
-        + CanonicalDeserialize;
+    type Output: Clone + Eq + Debug + Hash + Default + CanonicalSerialize + CanonicalDeserialize;
     type Parameters: Clone + CanonicalSerialize + CanonicalDeserialize + Sync;
 
     fn setup<R: Rng>(r: &mut R) -> Result<Self::Parameters, Error>;
diff --git a/crypto-primitives/src/crh/pedersen/constraints.rs b/crypto-primitives/src/crh/pedersen/constraints.rs
index 0d1e72ff..ce7aa49f 100644
--- a/crypto-primitives/src/crh/pedersen/constraints.rs
+++ b/crypto-primitives/src/crh/pedersen/constraints.rs
@@ -1,6 +1,6 @@
 use crate::crh::{
-    pedersen::{Parameters, Window},
-    CRHSchemeGadget as CRHGadgetTrait,
+    pedersen::{Parameters, TwoToOneCRH, Window, CRH},
+    CRHSchemeGadget as CRHGadgetTrait, CRHSchemeGadget, TwoToOneCRHSchemeGadget,
 };
 use ark_ec::CurveGroup;
 use ark_ff::Field;
@@ -8,10 +8,7 @@ use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::{Namespace, SynthesisError};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
-
-use crate::crh::pedersen::{TwoToOneCRH, CRH};
-use crate::crh::{CRHSchemeGadget, TwoToOneCRHSchemeGadget};
-use core::{borrow::Borrow, iter, marker::PhantomData};
+use ark_std::{borrow::Borrow, iter, marker::PhantomData};
 
 #[derive(Derivative)]
 #[derivative(Clone(bound = "C: CurveGroup, GG: CurveVar<C, ConstraintF<C>>"))]
diff --git a/crypto-primitives/src/crh/pedersen/mod.rs b/crypto-primitives/src/crh/pedersen/mod.rs
index 29d696d4..6fb1650f 100644
--- a/crypto-primitives/src/crh/pedersen/mod.rs
+++ b/crypto-primitives/src/crh/pedersen/mod.rs
@@ -1,20 +1,21 @@
-use crate::Error;
-use ark_std::rand::Rng;
-use ark_std::{
-    fmt::{Debug, Formatter, Result as FmtResult},
-    marker::PhantomData,
+use crate::{
+    crh::{CRHScheme, TwoToOneCRHScheme},
+    Error,
 };
-#[cfg(feature = "parallel")]
-use rayon::prelude::*;
-
-use crate::crh::{CRHScheme, TwoToOneCRHScheme};
 use ark_ec::CurveGroup;
 use ark_ff::{Field, ToConstraintField};
 use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use ark_std::borrow::Borrow;
-use ark_std::cfg_chunks;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{
+    borrow::Borrow,
+    cfg_chunks,
+    fmt::{Debug, Formatter, Result as FmtResult},
+    marker::PhantomData,
+    rand::Rng,
+};
+#[cfg(feature = "parallel")]
+use rayon::prelude::*;
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/crh/poseidon/constraints.rs b/crypto-primitives/src/crh/poseidon/constraints.rs
index 059a6934..ef7219ed 100644
--- a/crypto-primitives/src/crh/poseidon/constraints.rs
+++ b/crypto-primitives/src/crh/poseidon/constraints.rs
@@ -1,22 +1,25 @@
-use crate::crh::poseidon::{TwoToOneCRH, CRH};
-use crate::crh::CRHScheme;
-use crate::crh::{
-    CRHSchemeGadget as CRHGadgetTrait, TwoToOneCRHSchemeGadget as TwoToOneCRHGadgetTrait,
+use crate::{
+    crh::{
+        poseidon::{TwoToOneCRH, CRH},
+        CRHScheme, CRHSchemeGadget as CRHGadgetTrait,
+        TwoToOneCRHSchemeGadget as TwoToOneCRHGadgetTrait,
+    },
+    sponge::{
+        constraints::CryptographicSpongeVar,
+        poseidon::{constraints::PoseidonSpongeVar, PoseidonConfig},
+        Absorb,
+    },
 };
-use crate::sponge::constraints::CryptographicSpongeVar;
-use crate::sponge::poseidon::constraints::PoseidonSpongeVar;
-use crate::sponge::poseidon::PoseidonConfig;
-
-use crate::sponge::Absorb;
 use ark_ff::PrimeField;
-use ark_r1cs_std::alloc::{AllocVar, AllocationMode};
-use ark_r1cs_std::fields::fp::FpVar;
-use ark_r1cs_std::R1CSVar;
+use ark_r1cs_std::{
+    alloc::{AllocVar, AllocationMode},
+    fields::fp::FpVar,
+    R1CSVar,
+};
 use ark_relations::r1cs::{Namespace, SynthesisError};
-use ark_std::borrow::Borrow;
-use ark_std::marker::PhantomData;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{borrow::Borrow, marker::PhantomData};
 
 #[derive(Clone)]
 pub struct CRHParametersVar<F: PrimeField + Absorb> {
diff --git a/crypto-primitives/src/crh/poseidon/mod.rs b/crypto-primitives/src/crh/poseidon/mod.rs
index 6c465012..4b24e8cd 100644
--- a/crypto-primitives/src/crh/poseidon/mod.rs
+++ b/crypto-primitives/src/crh/poseidon/mod.rs
@@ -1,11 +1,13 @@
-use crate::crh::TwoToOneCRHScheme;
-use crate::sponge::poseidon::{PoseidonConfig, PoseidonSponge};
-use crate::sponge::{Absorb, CryptographicSponge};
-use crate::{crh::CRHScheme, Error};
+use crate::{
+    crh::{CRHScheme, TwoToOneCRHScheme},
+    sponge::{
+        poseidon::{PoseidonConfig, PoseidonSponge},
+        Absorb, CryptographicSponge,
+    },
+    Error,
+};
 use ark_ff::PrimeField;
-use ark_std::borrow::Borrow;
-use ark_std::marker::PhantomData;
-use ark_std::rand::Rng;
+use ark_std::{borrow::Borrow, marker::PhantomData, rand::Rng};
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/crh/sha256/constraints.rs b/crypto-primitives/src/crh/sha256/constraints.rs
index c68c97fd..6bee0060 100644
--- a/crypto-primitives/src/crh/sha256/constraints.rs
+++ b/crypto-primitives/src/crh/sha256/constraints.rs
@@ -4,9 +4,6 @@
 // Thank you!
 
 use crate::crh::{sha256::Sha256, CRHSchemeGadget, TwoToOneCRHSchemeGadget};
-
-use core::{borrow::Borrow, iter, marker::PhantomData};
-
 use ark_ff::PrimeField;
 use ark_r1cs_std::{
     alloc::{AllocVar, AllocationMode},
@@ -21,6 +18,7 @@ use ark_r1cs_std::{
 use ark_relations::r1cs::{ConstraintSystemRef, Namespace, SynthesisError};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{borrow::Borrow, iter, marker::PhantomData};
 
 const STATE_LEN: usize = 8;
 
diff --git a/crypto-primitives/src/crh/sha256/mod.rs b/crypto-primitives/src/crh/sha256/mod.rs
index 16738d88..d07b36ab 100644
--- a/crypto-primitives/src/crh/sha256/mod.rs
+++ b/crypto-primitives/src/crh/sha256/mod.rs
@@ -1,9 +1,11 @@
-use crate::crh::{CRHScheme, TwoToOneCRHScheme};
-use crate::Error;
-
-use ark_std::rand::Rng;
+use crate::{
+    crh::{CRHScheme, TwoToOneCRHScheme},
+    Error,
+};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{borrow::Borrow, rand::Rng};
+use sha2::digest::Digest;
 
 // Re-export the RustCrypto Sha256 type and its associated traits
 pub use sha2::{digest, Sha256};
@@ -12,10 +14,6 @@ pub use sha2::{digest, Sha256};
 pub mod constraints;
 
 // Implement the CRH traits for SHA-256
-
-use core::borrow::Borrow;
-use sha2::digest::Digest;
-
 impl CRHScheme for Sha256 {
     type Input = [u8];
     // This is always 32 bytes. It has to be a Vec to impl CanonicalSerialize
diff --git a/crypto-primitives/src/encryption/constraints.rs b/crypto-primitives/src/encryption/constraints.rs
index de2a8f91..503f733a 100644
--- a/crypto-primitives/src/encryption/constraints.rs
+++ b/crypto-primitives/src/encryption/constraints.rs
@@ -1,10 +1,8 @@
 use crate::encryption::AsymmetricEncryptionScheme;
-
+use ark_ff::fields::Field;
 use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::SynthesisError;
-use core::fmt::Debug;
-
-use ark_ff::fields::Field;
+use ark_std::fmt::Debug;
 
 pub trait AsymmetricEncryptionGadget<C: AsymmetricEncryptionScheme, ConstraintF: Field> {
     type OutputVar: AllocVar<C::Ciphertext, ConstraintF>
diff --git a/crypto-primitives/src/encryption/elgamal/constraints.rs b/crypto-primitives/src/encryption/elgamal/constraints.rs
index c5c3c21b..aa7b2a7f 100644
--- a/crypto-primitives/src/encryption/elgamal/constraints.rs
+++ b/crypto-primitives/src/encryption/elgamal/constraints.rs
@@ -1,15 +1,14 @@
-use ark_r1cs_std::prelude::*;
-use ark_relations::r1cs::{Namespace, SynthesisError};
-
-use crate::encryption::elgamal::{
-    Ciphertext, ElGamal, Parameters, Plaintext, PublicKey, Randomness,
+use crate::encryption::{
+    elgamal::{Ciphertext, ElGamal, Parameters, Plaintext, PublicKey, Randomness},
+    AsymmetricEncryptionGadget,
 };
-use crate::encryption::AsymmetricEncryptionGadget;
 use ark_ec::CurveGroup;
 use ark_ff::{
     fields::{Field, PrimeField},
     Zero,
 };
+use ark_r1cs_std::prelude::*;
+use ark_relations::r1cs::{Namespace, SynthesisError};
 use ark_serialize::CanonicalSerialize;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
diff --git a/crypto-primitives/src/encryption/elgamal/mod.rs b/crypto-primitives/src/encryption/elgamal/mod.rs
index 2ffc9563..107710c7 100644
--- a/crypto-primitives/src/encryption/elgamal/mod.rs
+++ b/crypto-primitives/src/encryption/elgamal/mod.rs
@@ -1,13 +1,10 @@
-#[cfg(feature = "r1cs")]
-pub mod constraints;
-
-use crate::encryption::AsymmetricEncryptionScheme;
-use crate::Error;
+use crate::{encryption::AsymmetricEncryptionScheme, Error};
 use ark_ec::{AdditiveGroup, CurveGroup};
 use ark_ff::{fields::PrimeField, UniformRand};
-use ark_std::marker::PhantomData;
-use ark_std::ops::Mul;
-use ark_std::rand::Rng;
+use ark_std::{marker::PhantomData, ops::Mul, rand::Rng};
+
+#[cfg(feature = "r1cs")]
+pub mod constraints;
 
 pub struct ElGamal<C: CurveGroup> {
     _group: PhantomData<C>,
diff --git a/crypto-primitives/src/encryption/mod.rs b/crypto-primitives/src/encryption/mod.rs
index d1213a76..5c721eb0 100644
--- a/crypto-primitives/src/encryption/mod.rs
+++ b/crypto-primitives/src/encryption/mod.rs
@@ -1,13 +1,12 @@
+use crate::Error;
+use ark_std::rand::Rng;
+
 #[cfg(feature = "r1cs")]
 pub mod constraints;
+pub mod elgamal;
 #[cfg(feature = "r1cs")]
 pub use constraints::*;
 
-pub mod elgamal;
-
-use crate::Error;
-use ark_std::rand::Rng;
-
 pub trait AsymmetricEncryptionScheme {
     type Parameters;
     type PublicKey;
diff --git a/crypto-primitives/src/lib.rs b/crypto-primitives/src/lib.rs
index 31ae920b..62d559b7 100644
--- a/crypto-primitives/src/lib.rs
+++ b/crypto-primitives/src/lib.rs
@@ -51,8 +51,8 @@ pub enum Error {
     SerializationError(ark_serialize::SerializationError),
 }
 
-impl core::fmt::Display for Error {
-    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+impl ark_std::fmt::Display for Error {
+    fn fmt(&self, f: &mut ark_std::fmt::Formatter<'_>) -> ark_std::fmt::Result {
         match self {
             Self::IncorrectInputLength(len) => write!(f, "incorrect input length: {len}"),
             Self::NotPrimeOrder => write!(f, "element is not prime order"),
diff --git a/crypto-primitives/src/merkle_tree/constraints.rs b/crypto-primitives/src/merkle_tree/constraints.rs
index aa9fbb87..83ae4f5b 100644
--- a/crypto-primitives/src/merkle_tree/constraints.rs
+++ b/crypto-primitives/src/merkle_tree/constraints.rs
@@ -1,13 +1,13 @@
-use crate::crh::TwoToOneCRHSchemeGadget;
-use crate::merkle_tree::{Config, IdentityDigestConverter};
-use crate::{crh::CRHSchemeGadget, merkle_tree::Path};
+use crate::{
+    crh::{CRHSchemeGadget, TwoToOneCRHSchemeGadget},
+    merkle_tree::{Config, IdentityDigestConverter, Path},
+};
 use ark_ff::PrimeField;
 use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::{Namespace, SynthesisError};
-use ark_std::borrow::Borrow;
-use ark_std::fmt::Debug;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{borrow::Borrow, fmt::Debug};
 
 pub trait DigestVarConverter<From, To: ?Sized> {
     type TargetType: Borrow<To>;
diff --git a/crypto-primitives/src/merkle_tree/mod.rs b/crypto-primitives/src/merkle_tree/mod.rs
index 5a7e4934..1a400452 100644
--- a/crypto-primitives/src/merkle_tree/mod.rs
+++ b/crypto-primitives/src/merkle_tree/mod.rs
@@ -1,27 +1,29 @@
 #![allow(clippy::needless_range_loop)]
 
-use core::hash::BuildHasherDefault;
-
 /// Defines a trait to chain two types of CRHs.
-use crate::crh::TwoToOneCRHScheme;
-use crate::sponge::Absorb;
-use crate::{crh::CRHScheme, Error};
+use crate::{
+    crh::{CRHScheme, TwoToOneCRHScheme},
+    sponge::Absorb,
+    Error,
+};
 use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use ark_std::borrow::Borrow;
-use ark_std::collections::BTreeSet;
-use ark_std::hash::Hash;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
+use ark_std::{
+    borrow::Borrow,
+    collections::BTreeSet,
+    fmt::Debug,
+    hash::{BuildHasherDefault, Hash},
+};
 use hashbrown::HashMap;
-
-#[cfg(test)]
-mod tests;
+#[cfg(feature = "parallel")]
+use rayon::prelude::*;
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
 
-#[cfg(feature = "parallel")]
-use rayon::prelude::*;
+#[cfg(test)]
+mod tests;
 
 #[cfg(all(
     target_has_atomic = "8",
@@ -83,7 +85,7 @@ pub trait Config {
                               // leaf layer
     type LeafDigest: Clone
         + Eq
-        + core::fmt::Debug
+        + Debug
         + Hash
         + Default
         + CanonicalSerialize
@@ -99,7 +101,7 @@ pub trait Config {
     // inner layer
     type InnerDigest: Clone
         + Eq
-        + core::fmt::Debug
+        + Debug
         + Hash
         + Default
         + CanonicalSerialize
@@ -222,13 +224,13 @@ impl<P: Config> Path<P> {
 ///  [I]J L  M
 /// ```
 ///  Suppose we want to prove I and J, then:
-///     `leaf_indexes` is: [2,3] (indexes in Merkle Tree leaves vector)
-///     `leaf_siblings_hashes`: [J,I]
-///     `auth_paths_prefix_lenghts`: [0,2]
-///     `auth_paths_suffixes`: [ [C,D], []]
+///     `leaf_indexes` is: `[2,3]` (indexes in Merkle Tree leaves vector)
+///     `leaf_siblings_hashes`: `[J,I]`
+///     `auth_paths_prefix_lenghts`: `[0,2]`
+///     `auth_paths_suffixes`: `[ [C,D], []]`
 ///  We can reconstruct the paths incrementally:
 ///  First, we reconstruct the first path. The prefix length is 0, hence we do not have any prefix encoding.
-///  The path is thus [C,D].
+///  The path is thus `[C,D]`.
 ///  Once the first path is verified, we can reconstruct the second path.
 ///  The prefix length of 2 means that the path prefix will be `previous_path[:2] -> [C,D]`.
 ///  Since the Merkle Tree branch is the same, the authentication path is the same (which means in this case that there is no suffix).
@@ -584,7 +586,9 @@ impl<P: Config> MerkleTree<P> {
     /// instead of
     /// `num_leaves*(num_leaves.log2()-1)`
     /// When verifying the proof, leaves hashes should be supplied in order, that is:
+    /// ```ignore
     /// let ordered_leaves: Vec<_> = self.leaf_indexes.into_iter().map(|i| leaves[i]).collect();
+    /// ```
     pub fn generate_multi_proof(
         &self,
         indexes: impl IntoIterator<Item = usize>,
diff --git a/crypto-primitives/src/merkle_tree/tests/constraints.rs b/crypto-primitives/src/merkle_tree/tests/constraints.rs
index 134e5092..ab55dc83 100644
--- a/crypto-primitives/src/merkle_tree/tests/constraints.rs
+++ b/crypto-primitives/src/merkle_tree/tests/constraints.rs
@@ -1,9 +1,11 @@
 mod byte_mt_tests {
-    use crate::crh::{pedersen, TwoToOneCRHScheme, TwoToOneCRHSchemeGadget};
-
-    use crate::crh::{CRHScheme, CRHSchemeGadget};
-    use crate::merkle_tree::constraints::{BytesVarDigestConverter, ConfigGadget};
-    use crate::merkle_tree::{constraints::PathVar, ByteDigestConverter, Config, MerkleTree};
+    use crate::crh::{
+        pedersen, CRHScheme, CRHSchemeGadget, TwoToOneCRHScheme, TwoToOneCRHSchemeGadget,
+    };
+    use crate::merkle_tree::{
+        constraints::{BytesVarDigestConverter, ConfigGadget, PathVar},
+        ByteDigestConverter, Config, MerkleTree,
+    };
     use ark_ed_on_bls12_381::{constraints::EdwardsVar, EdwardsProjective as JubJub, Fq};
     use ark_r1cs_std::prelude::*;
     use ark_relations::r1cs::ConstraintSystem;
@@ -234,13 +236,14 @@ mod byte_mt_tests {
 
 mod field_mt_tests {
     use crate::crh::{poseidon, CRHSchemeGadget, TwoToOneCRHSchemeGadget};
-    use crate::merkle_tree::constraints::ConfigGadget;
-    use crate::merkle_tree::tests::test_utils::poseidon_parameters;
-    use crate::merkle_tree::{constraints::PathVar, Config, IdentityDigestConverter, MerkleTree};
-    use ark_r1cs_std::fields::fp::FpVar;
-    use ark_r1cs_std::uint32::UInt32;
-    use ark_r1cs_std::R1CSVar;
-    use ark_r1cs_std::{alloc::AllocVar, convert::ToBitsGadget};
+    use crate::merkle_tree::{
+        constraints::{ConfigGadget, PathVar},
+        tests::test_utils::poseidon_parameters,
+        Config, IdentityDigestConverter, MerkleTree,
+    };
+    use ark_r1cs_std::{
+        alloc::AllocVar, convert::ToBitsGadget, fields::fp::FpVar, uint32::UInt32, R1CSVar,
+    };
     use ark_relations::r1cs::ConstraintSystem;
     use ark_std::{test_rng, One, UniformRand};
 
diff --git a/crypto-primitives/src/merkle_tree/tests/mod.rs b/crypto-primitives/src/merkle_tree/tests/mod.rs
index a2815f57..4f18d6eb 100644
--- a/crypto-primitives/src/merkle_tree/tests/mod.rs
+++ b/crypto-primitives/src/merkle_tree/tests/mod.rs
@@ -7,8 +7,7 @@ mod bytes_mt_tests {
     use crate::{crh::*, merkle_tree::*};
     use ark_ed_on_bls12_381::EdwardsProjective as JubJub;
     use ark_ff::BigInteger256;
-    use ark_std::{test_rng, UniformRand};
-    use std::iter::zip;
+    use ark_std::{iter::zip, test_rng, UniformRand};
 
     #[derive(Clone)]
     pub(super) struct Window4x256;
@@ -184,9 +183,12 @@ mod bytes_mt_tests {
 }
 
 mod field_mt_tests {
-    use crate::crh::poseidon;
-    use crate::merkle_tree::tests::test_utils::poseidon_parameters;
-    use crate::merkle_tree::{Config, IdentityDigestConverter, MerkleTree};
+    use crate::{
+        crh::poseidon,
+        merkle_tree::{
+            tests::test_utils::poseidon_parameters, Config, IdentityDigestConverter, MerkleTree,
+        },
+    };
     use ark_std::{test_rng, One, UniformRand};
 
     type F = ark_ed_on_bls12_381::Fr;
diff --git a/crypto-primitives/src/merkle_tree/tests/test_utils.rs b/crypto-primitives/src/merkle_tree/tests/test_utils.rs
index ef0795c6..9da40354 100644
--- a/crypto-primitives/src/merkle_tree/tests/test_utils.rs
+++ b/crypto-primitives/src/merkle_tree/tests/test_utils.rs
@@ -1,6 +1,5 @@
 use crate::sponge::poseidon::PoseidonConfig;
-use ark_std::str::FromStr;
-use ark_std::{One, Zero};
+use ark_std::{str::FromStr, One, Zero};
 
 type F = ark_ed_on_bls12_381::Fr;
 
diff --git a/crypto-primitives/src/prf/blake2s/constraints.rs b/crypto-primitives/src/prf/blake2s/constraints.rs
index cd9ea242..c0c180b9 100644
--- a/crypto-primitives/src/prf/blake2s/constraints.rs
+++ b/crypto-primitives/src/prf/blake2s/constraints.rs
@@ -1,13 +1,11 @@
-use ark_ff::PrimeField;
-use ark_relations::r1cs::{ConstraintSystemRef, Namespace, SynthesisError};
-
 use crate::prf::PRFGadget;
+use ark_ff::PrimeField;
 use ark_r1cs_std::prelude::*;
+use ark_relations::r1cs::{ConstraintSystemRef, Namespace, SynthesisError};
+use ark_std::borrow::Borrow;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
 
-use core::borrow::Borrow;
-
 // 2.1.  Parameters
 // The following table summarizes various parameters and their ranges:
 //               | BLAKE2b          | BLAKE2s          |
diff --git a/crypto-primitives/src/prf/blake2s/mod.rs b/crypto-primitives/src/prf/blake2s/mod.rs
index 7dd10c9b..5addc754 100644
--- a/crypto-primitives/src/prf/blake2s/mod.rs
+++ b/crypto-primitives/src/prf/blake2s/mod.rs
@@ -1,11 +1,9 @@
+use crate::{prf::PRF, Error};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
 use blake2::{Blake2s256 as B2s, Blake2sMac};
 use digest::Digest;
 
-use super::PRF;
-use crate::Error;
-
 #[cfg(feature = "r1cs")]
 pub mod constraints;
 
diff --git a/crypto-primitives/src/prf/constraints.rs b/crypto-primitives/src/prf/constraints.rs
index 19fb0da6..2e64729d 100644
--- a/crypto-primitives/src/prf/constraints.rs
+++ b/crypto-primitives/src/prf/constraints.rs
@@ -1,10 +1,8 @@
-use ark_ff::Field;
-use core::fmt::Debug;
-
 use crate::prf::PRF;
-use ark_relations::r1cs::{Namespace, SynthesisError};
-
+use ark_ff::Field;
 use ark_r1cs_std::prelude::*;
+use ark_relations::r1cs::{Namespace, SynthesisError};
+use ark_std::fmt::Debug;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
 
diff --git a/crypto-primitives/src/prf/mod.rs b/crypto-primitives/src/prf/mod.rs
index fa3da3a4..5aef9297 100644
--- a/crypto-primitives/src/prf/mod.rs
+++ b/crypto-primitives/src/prf/mod.rs
@@ -1,8 +1,7 @@
 #![allow(clippy::upper_case_acronyms)]
-use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
-use core::{fmt::Debug, hash::Hash};
-
 use crate::Error;
+use ark_serialize::{CanonicalDeserialize, CanonicalSerialize};
+use ark_std::{fmt::Debug, hash::Hash};
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/signature/constraints.rs b/crypto-primitives/src/signature/constraints.rs
index a669c0ad..860a8efb 100644
--- a/crypto-primitives/src/signature/constraints.rs
+++ b/crypto-primitives/src/signature/constraints.rs
@@ -1,9 +1,8 @@
+use crate::signature::SignatureScheme;
 use ark_ff::Field;
 use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::SynthesisError;
 
-use crate::signature::SignatureScheme;
-
 pub trait SigVerifyGadget<S: SignatureScheme, ConstraintF: Field> {
     type ParametersVar: AllocVar<S::Parameters, ConstraintF> + Clone;
 
diff --git a/crypto-primitives/src/signature/mod.rs b/crypto-primitives/src/signature/mod.rs
index 1f7cf219..577c6d73 100644
--- a/crypto-primitives/src/signature/mod.rs
+++ b/crypto-primitives/src/signature/mod.rs
@@ -1,7 +1,6 @@
 use crate::Error;
 use ark_serialize::CanonicalSerialize;
-use ark_std::hash::Hash;
-use ark_std::rand::Rng;
+use ark_std::{hash::Hash, rand::Rng};
 
 #[cfg(feature = "r1cs")]
 pub mod constraints;
diff --git a/crypto-primitives/src/signature/schnorr/constraints.rs b/crypto-primitives/src/signature/schnorr/constraints.rs
index 9198465f..f87089c3 100644
--- a/crypto-primitives/src/signature/schnorr/constraints.rs
+++ b/crypto-primitives/src/signature/schnorr/constraints.rs
@@ -1,15 +1,14 @@
+use crate::signature::{
+    schnorr::{Parameters, PublicKey, Schnorr},
+    SigRandomizePkGadget,
+};
 use ark_ec::CurveGroup;
 use ark_ff::Field;
 use ark_r1cs_std::prelude::*;
 use ark_relations::r1cs::{Namespace, SynthesisError};
-
-use crate::signature::SigRandomizePkGadget;
-
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
 use ark_std::{borrow::Borrow, marker::PhantomData};
-
-use crate::signature::schnorr::{Parameters, PublicKey, Schnorr};
 use digest::Digest;
 
 type ConstraintF<C> = <<C as CurveGroup>::BaseField as Field>::BasePrimeField;
diff --git a/crypto-primitives/src/signature/schnorr/mod.rs b/crypto-primitives/src/signature/schnorr/mod.rs
index bd7692f6..c27513f3 100644
--- a/crypto-primitives/src/signature/schnorr/mod.rs
+++ b/crypto-primitives/src/signature/schnorr/mod.rs
@@ -5,11 +5,9 @@ use ark_ff::{
     AdditiveGroup, One, ToConstraintField, UniformRand, Zero,
 };
 use ark_serialize::CanonicalSerialize;
-use ark_std::ops::Mul;
-use ark_std::rand::Rng;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
-use ark_std::{hash::Hash, marker::PhantomData};
+use ark_std::{hash::Hash, marker::PhantomData, ops::Mul, rand::Rng};
 use digest::Digest;
 
 #[cfg(feature = "r1cs")]
diff --git a/crypto-primitives/src/snark/constraints.rs b/crypto-primitives/src/snark/constraints.rs
index 92e16b92..ae4a39f0 100644
--- a/crypto-primitives/src/snark/constraints.rs
+++ b/crypto-primitives/src/snark/constraints.rs
@@ -1,17 +1,19 @@
 use ark_ff::{BigInteger, PrimeField};
-use ark_r1cs_std::fields::{
-    emulated_fp::{
-        params::{get_params, OptimizationType},
-        AllocatedEmulatedFpVar, EmulatedFpVar,
+use ark_r1cs_std::{
+    fields::{
+        emulated_fp::{
+            params::{get_params, OptimizationType},
+            AllocatedEmulatedFpVar, EmulatedFpVar,
+        },
+        fp::{AllocatedFp, FpVar},
     },
-    fp::{AllocatedFp, FpVar},
+    prelude::*,
 };
-use ark_r1cs_std::prelude::*;
-use ark_relations::r1cs::OptimizationGoal;
 use ark_relations::{
     lc, ns,
     r1cs::{
-        ConstraintSynthesizer, ConstraintSystemRef, LinearCombination, Namespace, SynthesisError,
+        ConstraintSynthesizer, ConstraintSystemRef, LinearCombination, Namespace, OptimizationGoal,
+        SynthesisError,
     },
 };
 use ark_snark::{CircuitSpecificSetupSNARK, UniversalSetupSNARK, SNARK};
@@ -30,9 +32,9 @@ pub trait SNARKGadget<F: PrimeField, ConstraintF: PrimeField, S: SNARK<F>> {
 
     /// Information about the R1CS constraints required to check proofs relative
     /// a given verification key. In the context of a LPCP-based pairing-based SNARK
-    /// like that of [[Groth16]](https://eprint.iacr.org/2016/260),
+    /// like that of [Groth16](https://eprint.iacr.org/2016/260),
     /// this is independent of the R1CS matrices,
-    /// whereas for more "complex" SNARKs like [[Marlin]](https://eprint.iacr.org/2019/1047),
+    /// whereas for more "complex" SNARKs like [Marlin](https://eprint.iacr.org/2019/1047),
     /// this can encode information about the highest degree of polynomials
     /// required to verify proofs.
     type VerifierSize: PartialOrd + Clone + fmt::Debug;
diff --git a/crypto-primitives/src/sponge/absorb.rs b/crypto-primitives/src/sponge/absorb.rs
index 60d83e85..b00a61a1 100644
--- a/crypto-primitives/src/sponge/absorb.rs
+++ b/crypto-primitives/src/sponge/absorb.rs
@@ -1,17 +1,16 @@
-use ark_ec::short_weierstrass::Affine as SWAffine;
-use ark_ec::twisted_edwards::Affine as TEAffine;
+pub use ark_crypto_primitives_macros::*;
 use ark_ec::{
-    short_weierstrass::SWCurveConfig as SWModelParameters,
-    twisted_edwards::TECurveConfig as TEModelParameters,
+    short_weierstrass::{Affine as SWAffine, SWCurveConfig as SWModelParameters},
+    twisted_edwards::{Affine as TEAffine, TECurveConfig as TEModelParameters},
+};
+use ark_ff::{
+    models::{Fp, FpConfig},
+    BigInteger, Field, PrimeField, ToConstraintField,
 };
-use ark_ff::models::{Fp, FpConfig};
-use ark_ff::{BigInteger, Field, PrimeField, ToConstraintField};
 use ark_serialize::CanonicalSerialize;
 #[cfg(not(feature = "std"))]
 use ark_std::{string::String, vec::Vec};
 
-pub use ark_crypto_primitives_macros::*;
-
 /// An interface for objects that can be absorbed by a `CryptographicSponge`.
 pub trait Absorb {
     /// Converts the object into a list of bytes that can be absorbed by a `CryptographicSponge`.
diff --git a/crypto-primitives/src/sponge/constraints/absorb.rs b/crypto-primitives/src/sponge/constraints/absorb.rs
index bb3abb4f..5235f164 100644
--- a/crypto-primitives/src/sponge/constraints/absorb.rs
+++ b/crypto-primitives/src/sponge/constraints/absorb.rs
@@ -3,15 +3,16 @@ use ark_ec::{
     twisted_edwards::TECurveConfig as TEModelParameters, CurveConfig as ModelParameters,
 };
 use ark_ff::{Field, PrimeField};
-use ark_r1cs_std::boolean::Boolean;
-use ark_r1cs_std::convert::{ToBytesGadget, ToConstraintFieldGadget};
-use ark_r1cs_std::fields::fp::FpVar;
-use ark_r1cs_std::fields::{FieldOpsBounds, FieldVar};
-use ark_r1cs_std::groups::curves::short_weierstrass::{
-    AffineVar as SWAffineVar, ProjectiveVar as SWProjectiveVar,
+use ark_r1cs_std::{
+    boolean::Boolean,
+    convert::{ToBytesGadget, ToConstraintFieldGadget},
+    fields::{fp::FpVar, FieldOpsBounds, FieldVar},
+    groups::curves::{
+        short_weierstrass::{AffineVar as SWAffineVar, ProjectiveVar as SWProjectiveVar},
+        twisted_edwards::AffineVar as TEAffineVar,
+    },
+    uint8::UInt8,
 };
-use ark_r1cs_std::groups::curves::twisted_edwards::AffineVar as TEAffineVar;
-use ark_r1cs_std::uint8::UInt8;
 use ark_relations::r1cs::SynthesisError;
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
@@ -213,9 +214,9 @@ impl<F: PrimeField, A: AbsorbGadget<F>> AbsorbGadget<F> for &A {
     }
 }
 
-/// Individually absorbs each element in a comma-separated list of [`Absorbable`]s into a sponge.
+/// Individually absorbs each element in a comma-separated list of [`AbsorbGadget`]s into a sponge.
 /// Format is `absorb!(s, a_0, a_1, ..., a_n)`, where `s` is a mutable reference to a sponge
-/// and each `a_i` implements `AbsorbableVar`.
+/// and each `a_i` implements [`AbsorbGadget`].
 #[macro_export]
 macro_rules! absorb_gadget {
     ($sponge:expr, $($absorbable:expr),+ ) => {
@@ -225,7 +226,7 @@ macro_rules! absorb_gadget {
     };
 }
 
-/// Quickly convert a list of different [`Absorbable`]s into sponge field elements.
+/// Quickly convert a list of different [`AbsorbGadget`]s into sponge field elements.
 #[macro_export]
 macro_rules! collect_sponge_field_elements_gadget {
     ($head:expr $(, $tail:expr)* ) => {
diff --git a/crypto-primitives/src/sponge/constraints/mod.rs b/crypto-primitives/src/sponge/constraints/mod.rs
index aa872fe5..51acebb1 100644
--- a/crypto-primitives/src/sponge/constraints/mod.rs
+++ b/crypto-primitives/src/sponge/constraints/mod.rs
@@ -1,14 +1,22 @@
 use crate::sponge::{Absorb, CryptographicSponge, FieldElementSize};
 use ark_ff::PrimeField;
-use ark_r1cs_std::alloc::AllocVar;
-use ark_r1cs_std::boolean::Boolean;
-use ark_r1cs_std::fields::emulated_fp::params::{get_params, OptimizationType};
-use ark_r1cs_std::fields::emulated_fp::{AllocatedEmulatedFpVar, EmulatedFpVar};
-use ark_r1cs_std::fields::fp::{AllocatedFp, FpVar};
-use ark_r1cs_std::uint8::UInt8;
-use ark_r1cs_std::R1CSVar;
-use ark_relations::lc;
-use ark_relations::r1cs::{ConstraintSystemRef, LinearCombination, SynthesisError};
+use ark_r1cs_std::{
+    alloc::AllocVar,
+    boolean::Boolean,
+    fields::{
+        emulated_fp::{
+            params::{get_params, OptimizationType},
+            AllocatedEmulatedFpVar, EmulatedFpVar,
+        },
+        fp::{AllocatedFp, FpVar},
+    },
+    uint8::UInt8,
+    R1CSVar,
+};
+use ark_relations::{
+    lc,
+    r1cs::{ConstraintSystemRef, LinearCombination, SynthesisError},
+};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
 
diff --git a/crypto-primitives/src/sponge/merlin/mod.rs b/crypto-primitives/src/sponge/merlin/mod.rs
new file mode 100644
index 00000000..47906dee
--- /dev/null
+++ b/crypto-primitives/src/sponge/merlin/mod.rs
@@ -0,0 +1,33 @@
+use crate::sponge::{Absorb, CryptographicSponge};
+#[cfg(not(feature = "std"))]
+use ark_std::vec::Vec;
+pub use merlin::Transcript;
+
+impl CryptographicSponge for Transcript {
+    type Config = &'static [u8];
+
+    fn new(params: &Self::Config) -> Self {
+        Transcript::new(*params)
+    }
+
+    fn absorb(&mut self, input: &impl Absorb) {
+        self.append_message(b"", &input.to_sponge_bytes_as_vec());
+    }
+
+    fn squeeze_bytes(&mut self, num_bytes: usize) -> Vec<u8> {
+        let mut dest = vec![0; num_bytes];
+        self.challenge_bytes(b"", &mut dest);
+        dest
+    }
+
+    fn squeeze_bits(&mut self, num_bits: usize) -> Vec<bool> {
+        let num_bytes = (num_bits + 7) / 8;
+        let mut tmp = vec![0; num_bytes];
+        self.challenge_bytes(b"", &mut tmp);
+        let dest = tmp
+            .iter()
+            .flat_map(|byte| (0..8u32).rev().map(move |i| (byte >> i) & 1 == 1))
+            .collect::<Vec<_>>();
+        dest[..num_bits].to_vec()
+    }
+}
diff --git a/crypto-primitives/src/sponge/mod.rs b/crypto-primitives/src/sponge/mod.rs
index 2356f169..47a2c202 100644
--- a/crypto-primitives/src/sponge/mod.rs
+++ b/crypto-primitives/src/sponge/mod.rs
@@ -17,6 +17,11 @@ pub use absorb::*;
 /// [cos]: https://eprint.iacr.org/2019/1076
 pub mod poseidon;
 
+/// The sponge for [Merlin][merlin]
+///
+/// [merlin]: https://merlin.cool/
+pub mod merlin;
+
 #[cfg(test)]
 mod test;
 
diff --git a/crypto-primitives/src/sponge/poseidon/constraints.rs b/crypto-primitives/src/sponge/poseidon/constraints.rs
index fc0409ac..60aa800b 100644
--- a/crypto-primitives/src/sponge/poseidon/constraints.rs
+++ b/crypto-primitives/src/sponge/poseidon/constraints.rs
@@ -1,11 +1,10 @@
-use crate::sponge::constraints::AbsorbGadget;
-use crate::sponge::constraints::{CryptographicSpongeVar, SpongeWithGadget};
-use crate::sponge::poseidon::{PoseidonConfig, PoseidonSponge};
-use crate::sponge::DuplexSpongeMode;
-
+use crate::sponge::{
+    constraints::{AbsorbGadget, CryptographicSpongeVar, SpongeWithGadget},
+    poseidon::{PoseidonConfig, PoseidonSponge},
+    DuplexSpongeMode,
+};
 use ark_ff::PrimeField;
-use ark_r1cs_std::fields::fp::FpVar;
-use ark_r1cs_std::prelude::*;
+use ark_r1cs_std::{fields::fp::FpVar, prelude::*};
 use ark_relations::r1cs::{ConstraintSystemRef, SynthesisError};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;
@@ -169,12 +168,13 @@ impl<F: PrimeField> PoseidonSpongeVar<F> {
                     ..(self.parameters.capacity + num_elements_squeezed + rate_start_index)],
             );
 
+            // Repeat with updated output slices and rate start index
+            remaining_output = &mut remaining_output[num_elements_squeezed..];
+
             // Unless we are done with squeezing in this call, permute.
-            if remaining_output.len() != self.parameters.rate {
+            if !remaining_output.is_empty() {
                 self.permute()?;
             }
-            // Repeat with updated output slices and rate start index
-            remaining_output = &mut remaining_output[num_elements_squeezed..];
             rate_start_index = 0;
         }
     }
@@ -223,7 +223,6 @@ impl<F: PrimeField> CryptographicSpongeVar<F, PoseidonSponge<F>> for PoseidonSpo
             DuplexSpongeMode::Squeezing {
                 next_squeeze_index: _,
             } => {
-                self.permute()?;
                 self.absorb_internal(0, input.as_slice())?;
             }
         };
diff --git a/crypto-primitives/src/sponge/poseidon/mod.rs b/crypto-primitives/src/sponge/poseidon/mod.rs
index eee18b93..471c1622 100644
--- a/crypto-primitives/src/sponge/poseidon/mod.rs
+++ b/crypto-primitives/src/sponge/poseidon/mod.rs
@@ -174,12 +174,13 @@ impl<F: PrimeField> PoseidonSponge<F> {
                     ..(self.parameters.capacity + num_elements_squeezed + rate_start_index)],
             );
 
+            // Repeat with updated output slices
+            output_remaining = &mut output_remaining[num_elements_squeezed..];
             // Unless we are done with squeezing in this call, permute.
-            if output_remaining.len() != self.parameters.rate {
+            if !output_remaining.is_empty() {
                 self.permute();
             }
-            // Repeat with updated output slices
-            output_remaining = &mut output_remaining[num_elements_squeezed..];
+
             rate_start_index = 0;
         }
     }
@@ -250,7 +251,6 @@ impl<F: PrimeField> CryptographicSponge for PoseidonSponge<F> {
             DuplexSpongeMode::Squeezing {
                 next_squeeze_index: _,
             } => {
-                self.permute();
                 self.absorb_internal(0, elems.as_slice());
             }
         };
diff --git a/crypto-primitives/src/sponge/poseidon/tests.rs b/crypto-primitives/src/sponge/poseidon/tests.rs
index cc44fd73..337caf7f 100644
--- a/crypto-primitives/src/sponge/poseidon/tests.rs
+++ b/crypto-primitives/src/sponge/poseidon/tests.rs
@@ -1,10 +1,244 @@
-use crate::sponge::poseidon::{PoseidonConfig, PoseidonSponge};
-use crate::sponge::test::Fr;
-use crate::sponge::{Absorb, AbsorbWithLength, CryptographicSponge, FieldBasedCryptographicSponge};
-use crate::{absorb, collect_sponge_bytes, collect_sponge_field_elements};
+use crate::{
+    absorb, collect_sponge_bytes, collect_sponge_field_elements,
+    sponge::{
+        poseidon::{PoseidonConfig, PoseidonDefaultConfigField, PoseidonSponge},
+        test::Fr,
+        Absorb, AbsorbWithLength, CryptographicSponge, FieldBasedCryptographicSponge,
+    },
+};
 use ark_ff::{One, PrimeField, UniformRand};
 use ark_std::test_rng;
 
+#[test]
+// Remove once this PR matures
+fn demo_bug() {
+    let sponge_params = Fr::get_default_poseidon_parameters(2, false).unwrap();
+
+    let rng = &mut test_rng();
+    let input = (0..3).map(|_| Fr::rand(rng)).collect::<Vec<_>>();
+
+    // works good
+    let e0 = {
+        let mut sponge = PoseidonSponge::<Fr>::new(&sponge_params);
+        sponge.absorb(&input);
+        sponge.squeeze_native_field_elements(3)
+    };
+
+    // works good
+    let e1 = {
+        let mut sponge = PoseidonSponge::<Fr>::new(&sponge_params);
+        sponge.absorb(&input);
+        let e0 = sponge.squeeze_native_field_elements(1);
+        let e1 = sponge.squeeze_native_field_elements(1);
+        let e2 = sponge.squeeze_native_field_elements(1);
+        e0.iter()
+            .chain(e1.iter())
+            .chain(e2.iter())
+            .cloned()
+            .collect::<Vec<_>>()
+    };
+
+    // also works good
+    let e2 = {
+        let mut sponge = PoseidonSponge::<Fr>::new(&sponge_params);
+        sponge.absorb(&input);
+
+        let e0 = sponge.squeeze_native_field_elements(2);
+        let e1 = sponge.squeeze_native_field_elements(1);
+        e0.iter().chain(e1.iter()).cloned().collect::<Vec<_>>()
+    };
+
+    // skips a permutation if sponge
+    // * in squeezing mode
+    // * number of elements are equal to rate
+    let e3 = {
+        let mut sponge = PoseidonSponge::<Fr>::new(&sponge_params);
+        sponge.absorb(&input);
+        let e0 = sponge.squeeze_native_field_elements(1);
+        let e1 = sponge.squeeze_native_field_elements(2);
+        e0.iter().chain(e1.iter()).cloned().collect::<Vec<_>>()
+    };
+
+    assert_eq!(e0, e1);
+    assert_eq!(e0, e2);
+    assert_eq!(e0, e3); // this will fail
+}
+
+// Remove once this PR matures
+fn run_cross_test<F: PrimeField + Absorb>(cfg: &PoseidonConfig<F>) {
+    #[derive(Debug, PartialEq, Eq)]
+    enum SpongeMode {
+        Absorbing,
+        Squeezing,
+    }
+
+    #[derive(Clone, Debug)]
+    struct Reference<F: PrimeField> {
+        cfg: PoseidonConfig<F>,
+        state: Vec<F>,
+        absorbing: Vec<F>,
+        squeeze_count: Option<usize>,
+    }
+
+    // workaround to permute a state
+    fn permute<F: PrimeField>(cfg: &PoseidonConfig<F>, state: &mut [F]) {
+        let mut sponge = PoseidonSponge::new(&cfg);
+        sponge.state.copy_from_slice(state);
+        sponge.permute();
+        state.copy_from_slice(&sponge.state)
+    }
+
+    impl<F: PrimeField> Reference<F> {
+        fn new(cfg: &PoseidonConfig<F>) -> Self {
+            let t = cfg.rate + cfg.capacity;
+            let state = vec![F::zero(); t];
+            Self {
+                cfg: cfg.clone(),
+                state,
+                absorbing: Vec::new(),
+                squeeze_count: None,
+            }
+        }
+
+        fn mode(&self) -> SpongeMode {
+            match self.squeeze_count {
+                Some(_) => {
+                    assert!(self.absorbing.is_empty());
+                    SpongeMode::Squeezing
+                }
+                None => SpongeMode::Absorbing,
+            }
+        }
+
+        fn absorb(&mut self, input: &[F]) {
+            if !input.is_empty() {
+                match self.mode() {
+                    SpongeMode::Absorbing => self.absorbing.extend_from_slice(input),
+                    SpongeMode::Squeezing => {
+                        // Append inputs to the absorbing line
+                        self.absorbing.extend_from_slice(input);
+                        // Change mode to absorbing
+                        self.squeeze_count = None;
+                    }
+                }
+            }
+        }
+
+        fn _absorb(&mut self) {
+            let rate = self.cfg.rate;
+            self.absorbing.chunks(rate).for_each(|chunk| {
+                self.state
+                    .iter_mut()
+                    .skip(self.cfg.capacity)
+                    .zip(chunk.iter())
+                    .for_each(|(s, c)| *s += *c);
+                permute(&self.cfg, &mut self.state);
+            });
+
+            // This case can only happen in the begining when the absorbing line is empty
+            // and user wants to squeeze elements. Notice that after moving to squueze mode
+            // if user calls absorb again with empty input it will be ignored
+            self.absorbing
+                .is_empty()
+                .then(|| permute(&self.cfg, &mut self.state));
+
+            // flush the absorbing line
+            self.absorbing.clear();
+
+            // Change to the squeezing mode
+            assert_eq!(self.mode(), SpongeMode::Absorbing);
+            self.squeeze_count = Some(0);
+        }
+
+        pub fn squeeze(&mut self, n: usize) -> Vec<F> {
+            match self.mode() {
+                SpongeMode::Absorbing => self._absorb(),
+                SpongeMode::Squeezing => {
+                    assert!(self.absorbing.is_empty());
+                    assert!(self.squeeze_count.is_some());
+
+                    // ???
+                    // **This seems nonsense to me**
+                    // If,
+                    //    * number of squeeze is zero AND
+                    //    * in squeezing mode AND
+                    //    * output index is is at `rate`
+                    // it applies a useless permutation.
+                    // This is also not appied in SAFE sponge
+
+                    if n == 0 {
+                        let squeeze_count = self.squeeze_count.unwrap();
+                        let out_index = self.squeeze_count.unwrap() % self.cfg.rate;
+                        (out_index == 0 && squeeze_count != 0).then(|| {
+                            permute(&self.cfg, &mut self.state);
+                            self.squeeze_count = Some(0);
+                        });
+                    }
+                }
+            }
+
+            let rate = self.cfg.rate;
+            let mut output = Vec::new();
+            for _ in 0..n {
+                let squeeze_count = self.squeeze_count.unwrap();
+                let out_index = squeeze_count % rate;
+
+                // proceed with a permutation if
+                // * the rate is full
+                // * and it is not the first output
+                (out_index == 0 && squeeze_count != 0).then(|| permute(&self.cfg, &mut self.state));
+
+                // skip the capacity elements
+                let out_index = out_index + self.cfg.capacity;
+                output.push(self.state[out_index]);
+                self.squeeze_count.as_mut().map(|c| *c += 1);
+            }
+
+            output
+        }
+    }
+
+    let mut sponge = PoseidonSponge::new(cfg);
+    let mut sponge_ref = Reference::new(cfg);
+    let mut rng = test_rng();
+
+    for _ in 0..1000 {
+        let test = (0..100)
+            .map(|_| {
+                use crate::ark_std::rand::Rng;
+                let do_absorb = rng.gen_bool(0.5);
+                let do_squeeze = rng.gen_bool(0.5);
+
+                (
+                    (do_absorb, rng.gen_range(0..=cfg.rate * 2 + 1)),
+                    (do_squeeze, rng.gen_range(0..=cfg.rate * 2 + 1)),
+                )
+            })
+            .collect::<Vec<_>>();
+
+        // fuzz fuzz
+        for (_i, ((do_absorb, n_absorb), (do_squeeze, n_squeeze))) in test.into_iter().enumerate() {
+            do_absorb.then(|| {
+                let inputs = (0..n_absorb).map(|_| F::rand(&mut rng)).collect::<Vec<_>>();
+                sponge_ref.absorb(&inputs);
+                sponge.absorb(&inputs);
+            });
+            do_squeeze.then(|| {
+                let out0 = sponge_ref.squeeze(n_squeeze);
+                let out1 = sponge.squeeze_field_elements(n_squeeze);
+                assert_eq!(out0, out1);
+            });
+        }
+    }
+}
+
+#[test]
+// Remove once this PR matures
+fn test_cross() {
+    let cfg = Fr::get_default_poseidon_parameters(2, false).unwrap();
+    run_cross_test::<Fr>(&cfg);
+}
+
 fn assert_different_encodings<F: PrimeField, A: Absorb>(a: &A, b: &A) {
     let bytes1 = a.to_sponge_bytes_as_vec();
     let bytes2 = b.to_sponge_bytes_as_vec();
diff --git a/crypto-primitives/src/sponge/poseidon/traits.rs b/crypto-primitives/src/sponge/poseidon/traits.rs
index c1c446e7..bfe10fed 100644
--- a/crypto-primitives/src/sponge/poseidon/traits.rs
+++ b/crypto-primitives/src/sponge/poseidon/traits.rs
@@ -1,5 +1,4 @@
-use crate::sponge::poseidon::grain_lfsr::PoseidonGrainLFSR;
-use crate::sponge::poseidon::PoseidonConfig;
+use crate::sponge::poseidon::{grain_lfsr::PoseidonGrainLFSR, PoseidonConfig};
 use ark_ff::{fields::models::*, PrimeField};
 #[cfg(not(feature = "std"))]
 use ark_std::vec::Vec;