py-shannon

Pure Python implementation of Shannon stream cipher. No-brainer port of shannon.

Shannon cipher is used in Spotify Connect to encrypt communication between player and Spotify AP server. Shannon cipher is variant of Sober stream cipher.

Example

Encryption

from shannon import Shannon

key = b"\x65\x87\xd8\x8f\x6c\x32\x9d\x8a\xe4\x6b"
message = "My secret message".encode("utf-8")

shannon = Shannon(key)

message = shannon.encrypt(message)  # -> bytes
# message contains ciphertext now
mac = shannon.finish()  # -> bytes
# mac contains MAC of the message

Decryption

from shannon import Shannon

key = b"\x65\x87\xd8\x8f\x6c\x32\x9d\x8a\xe4\x6b"
# message is encrypted
message = b"\x91\x9d\xa9\xb6\x29\xfc\x9c\xdd\x17\x8c\x15\x31\x9a\xae\xcc\x6e\xd4"
received_mac = b"\xbe\x7b\xef\x39\xee\xfe\x54\xfd\x8d\xb0\xbc\x6f\xd5\x30\x35\x19"

shannon = Shannon(key)
message = shannon.decrypt(message)  # -> bytes
# message contains plaintext now
mac = shannon.finish()
if mac == received_mac:
    print("MAC OK")