• A simple client server model which performs a key exchange using a simplistic Diffie Hellman and then by using the key it performs shift cipher on remaining communication.
• Key is temporary to all sessions.
• Code is written in Python

Multithreaded server which provides login, register and file download features.

$ ./server.sh

Client which provides login, register and file download features. It runs a main loop to take user input and provides a mini shell to list and download files on server.

$ ./server.sh [ IP address of server ]

• password.db - Will hold user credentials for backup and loading.
• client.log - maintains a log session for client operations.
• server.log - maintains a log session for server operations.
• crypto.log - maintains a log for all calls to sendSecure and recvSecure
• client.py and server.py - main code.
• uploads/ - This is the directory it creates or checks which will be used to server files.

Performs operations related to all shift operations and provides wrapper for securely send() and write()

• code - automatically detects the type of input and returns code or decoded value.
• ROT - takes k, s, delim which is key, string to shift and delimiter to skip.
• UNROT - takes k, s, delim which is key, string to unshift and delimiter to skip.
• sendSecure - takes a socket, key to call ROT, plaintext and delimiter. Sends encrypted text over this passed socket.
• recvSecure - takes a socket, key to call UNROT, ciphertext and delimiter. Receives encrypted text over this passed socket and returns plaintext.

Takes care of initial key change and appropriate calls to prime module

• randomPrime - returns a random prime
• generateAlpha - takes a prime and returns it primitive root
• genPrivateKey - generates a private key from prime and primitive root.
• genKeyDerivation - derives the session key after parameter exchange.
• initKeyExchg - takes a socket and inits key exchange over it.
• performKeyExchg - takes a socket and performs key exchange over it.

provides utility function for file directory viewing.

• directoryList - returns list of files in serving directory

all forms of packet creation is done via this module

• createLoginRequest - Packet for User registration
• createLoginReply - Packet for User registration
• createAuthRequest - Packet for User Authentication
• createAuthReply- Packet for User Authentication
• createServiceRequest - Packet for Service Request
• createServiceDone - Packet for Service Completion
• packMessage - Trivial serialization
• unpackMessage - Trivial unserialization

provides extremely basic logging capabilities

• minilogger.writer - append or fresh log file operations

interface to password.db file and in memory structure

• isUserExist - test if user already registered.
• adduserpasswordDB - add user to system
• testauthpasswordDB - during authentication perform hash check
• loadPasswordDB - on start of server loads password.db file in memory
• dumpPasswordDB - flushed passwords on to password.db file on each new entry

module to perform all prime number calculcations

• is_prime - test if prime or not
• generate_prime_number - returns a prime number
• generate_prime_candidate - limits the bound for prime number
• prim_root - calculates primitive root of the prime number provided