zevlee / footprint-otp Goto Github PK

One-time-pad is a bit of an odd bird in the world of cryptography, as it has exact requirements

1. The pad must be truly random. In other words, you can not use any algorithm to create the one-time pad, but a HWRNG. Your application is using the secrets.token_bytes() method, which is a wrapper for os.urandom() which in turn reads from the kernel CSPRNG algorithm. the PR in CSPRNG stand's for pseudo-random, which is not the same.

2. One-time pad is an optimal cipher among the ciphers that provide perfect secrecy, as it satisfies the "key must be at least as long as the message" condition with equality. The kernel CSPRNG is usually seeded from the CPU's HWRNG and/or the chaotic events (interrupt events etc.) that happen during the use, but as the kernel CSPRNG expands the computationally secure seed, it does not provide perfect secrecy, only computational security.

XORing plaintext with keystream is what all stream ciphers do. Since the kernel CSPRNG is ChaCha20 stream cipher on Linux and AES on Windows, you're effectively using either ChaCha20 or AES encryption, with pre-shared keystream.

Please strongly consider removing all references to OTP, or change the system to utilize a hardware random number generator.

https://github.com/zevlee/footprint-otp/blob/main/lib/otp.py#L48 shows the software is XORing plaintext with the keystream, without adding message authentication code to the message. This makes the ciphertext vulnerable to known plaintext attacks (KPA), where if the attacker knows the plaintext for any reason, they're able to obtain key with key = ciphertext XOR plaintext, and they can then substitute message with their own by passing new_ciphertext = new_plaintext XOR key to the recipient.

Because of the recent change in pyinstaller version 6.0.0 to restructure onedir builds pyinstaller/pyinstaller#7713, the build scripts do not currently work. This will be addressed in an upcoming fix.