nim_chacha20_poly1305

A pure nim library implementing:

• Chacha20
• poly1305
• chacha20_poly1305
• xchacha20_poly1305

⚠️ This is WIP and needs review ⚠️

• This project was created for learning.
• It needs to be reviewed and users should think & review before using.
• Vunrable to side channel attacks on the POLY function

TODO

• chacha20
  • quarter round
  • quarter rounds
  • inner block
  • add block
  • serialize block
  • chacha20_init
  • chacha_xor
• poly1305
  • poly_pad
  • poly_init
  • poly_update
  • poly_finalize - don't need at the moment
• chacha20_poly1305
  • chacha20_poly1305_encrypt
  • chacha20_poly1305_decrypt
  • chacha20_poly1305_verify - dont need atm
• xchacha20_poly1305
  • hchacha20_init
  • hchacha20
• streams
• factory that gives chacha(n) rounds
• add more test vectors
• make style more uniform
• add helpers byte[] <-> string <-> hex[]
• add runable examples?

Resources & References

chacha20

• https://datatracker.ietf.org/doc/html/rfc7539

note xchacha, as of 2022 still in draft

• https://datatracker.ietf.org/doc/html/draft-arciszewski-xchacha-03
• https://www.ietf.org/archive/id/draft-irtf-cfrg-xchacha-03.txt

another chacha20 implementation:

• https://git.sr.ht/~ehmry/chacha20

Usage

import  nim_chacha20_poly1305/[common, chacha20, poly1305, xchacha20_poly1305]

export common
export chacha20
export poly1305
export xchacha20_poly1305

import std/sysrand

proc main() =
    var
        key_in: Key = [
            0x80'u8, 0x81'u8, 0x82'u8, 0x83'u8, 0x84'u8, 0x85'u8, 0x86'u8, 0x87'u8, 0x88'u8, 0x89'u8, 0x8a'u8, 0x8b'u8, 0x8c'u8, 0x8d'u8, 0x8e'u8, 0x8f'u8,
            0x90'u8, 0x91'u8, 0x92'u8, 0x93'u8, 0x94'u8, 0x95'u8, 0x96'u8, 0x97'u8, 0x98'u8, 0x99'u8, 0x9a'u8, 0x9b'u8, 0x9c'u8, 0x9d'u8, 0x9e'u8, 0x9f'u8,
        ]
        nonce_in: XNonce
        encrypt_counter: Counter
        decrypt_counter: Counter
        # Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it.
        plain_data: array[114, byte] = [
            0x4c'u8, 0x61'u8, 0x64'u8, 0x69'u8, 0x65'u8, 0x73'u8, 0x20'u8, 0x61'u8, 0x6e'u8, 0x64'u8, 0x20'u8, 0x47'u8, 0x65'u8, 0x6e'u8, 0x74'u8, 0x6c'u8,
            0x65'u8, 0x6d'u8, 0x65'u8, 0x6e'u8, 0x20'u8, 0x6f'u8, 0x66'u8, 0x20'u8, 0x74'u8, 0x68'u8, 0x65'u8, 0x20'u8, 0x63'u8, 0x6c'u8, 0x61'u8, 0x73'u8,
            0x73'u8, 0x20'u8, 0x6f'u8, 0x66'u8, 0x20'u8, 0x27'u8, 0x39'u8, 0x39'u8, 0x3a'u8, 0x20'u8, 0x49'u8, 0x66'u8, 0x20'u8, 0x49'u8, 0x20'u8, 0x63'u8,
            0x6f'u8, 0x75'u8, 0x6c'u8, 0x64'u8, 0x20'u8, 0x6f'u8, 0x66'u8, 0x66'u8, 0x65'u8, 0x72'u8, 0x20'u8, 0x79'u8, 0x6f'u8, 0x75'u8, 0x20'u8, 0x6f'u8,
            0x6e'u8, 0x6c'u8, 0x79'u8, 0x20'u8, 0x6f'u8, 0x6e'u8, 0x65'u8, 0x20'u8, 0x74'u8, 0x69'u8, 0x70'u8, 0x20'u8, 0x66'u8, 0x6f'u8, 0x72'u8, 0x20'u8,
            0x74'u8, 0x68'u8, 0x65'u8, 0x20'u8, 0x66'u8, 0x75'u8, 0x74'u8, 0x75'u8, 0x72'u8, 0x65'u8, 0x2c'u8, 0x20'u8, 0x73'u8, 0x75'u8, 0x6e'u8, 0x73'u8,
            0x63'u8, 0x72'u8, 0x65'u8, 0x65'u8, 0x6e'u8, 0x20'u8, 0x77'u8, 0x6f'u8, 0x75'u8, 0x6c'u8, 0x64'u8, 0x20'u8, 0x62'u8, 0x65'u8, 0x20'u8, 0x69'u8,
            0x74'u8, 0x2e'u8
        ]   
        auth_data_in = [
            0x50'u8, 0x51'u8, 0x52'u8, 0x53'u8, 0xc0'u8, 0xc1'u8, 0xc2'u8, 0xc3'u8, 0xc4'u8, 0xc5'u8, 0xc6'u8, 0xc7'u8,
        ]
        cipher_data_decrypted: array[114, byte]
        tag_out: Tag
        tag_expected: Tag 
        cipher_data_expected: array[114, byte]

    encrypt_counter = decrypt_counter
    discard urandom(nonce_in)
    xchacha20_aead_poly1305_encrypt(
        key_in,
        nonce_in,
        encrypt_counter,
        auth_data_in,
        plain_data,
        cipher_data_expected,
        tag_expected
    )

    xchacha20_aead_poly1305_decrypt(
        key_in,
        nonce_in,
        decrypt_counter,
        auth_data_in,
        cipher_data_decrypted,
        cipher_data_expected,
        tag_out
    )
    if tag_out != tag_expected:
        echo "MESSAGE IS POISONED"
    
    echo $$$cipher_data_decrypted

when isMainModule:
    main()