CS6500 - Assignment 3

KDC based key establishment

The objective of this assignment is to implement the KDC-based key establishment (exchange) for use with symmetric key encryption algorithms. The data encryption algorithm to be used for client-client and KDC-client communication is: AES-128-CBC, i.e. 128-bit key with CBC mode.

We have implemented 3 roles here:

1. KDC-server

This acts as the center on which users register with their ID and Address. Each user also has aa unique master key shared with the server, which is used to generate a shared key between a specific user and the server.
Any registered user (say A) can query this KDC server to get the address and a session key of another registered user (say B) and some enrypted data which proves authenticity of user A to user B. Also a session key is generated to share data from A to B.
The arguments are as provided in the assignment statement. Example run:

$ python3 kdc.py -p 12345 -o logs.txt -f pwd.txt

Here:
12345 - is the port on which the server listens to.
out.txt - is the log file.
pwd.txt - is the file in which the server stores the details of registered users.

2. Client (Sender type)

After regisitering with the KDC server, this type of client wishes to get the details of another registered user so that they can send some message/file.
The arguments are as provided in the assignment statement. Example run:

$ python3 client.py -n alice -m S -o bob -i inp.txt -a 127.0.0.1 -p 12345

Here:
alice - is the name/ID of the user.
S - signifies that the program acts as a sender.
bob - is the name of the person alice wants to send file to.
inp.txt - is the file to be sent to bob.
127.0.0.1 - the IP of KDC server.
12345 - the PORT number of KDC server

3. Client (Receiver type)

After registration with KDC server, this type of client listens to the registered port and waits for encrypted messages from other usuers.
The arguments are as provided in the assignment statement. Example run:

$ python3 client.py -n bob -m R -s out_enc.txt -o out.txt -a 127.0.0.1 -p 12345

Here:
bob - is the name/ID of use.
R - signifies that the program acts as receiver client.
out_enc.txt - file where the encrypted message is stored in base64 encoding.
out.txt - file where message is stored after decryption.
127.0.0.1 - the IP of KDC server.
12345 - the port of KDC server.

TYPESCRIPTS

Experimented with 3 terminal windows, one corresponding to a example run given above. Terrminal typescripts are recorded with the above example instance. Attached inside the typescripts folder.
First start the server program. Then start the client programs. Used

$ col -bp < bin_file > file.txt

to convert the binary files into readable text format.