Technical Notes

General Technical Notes

• Objects are encrypted in memory prior to writing to file
• encrypt()/decrypt() can process any R object understood by serialize()

The encryption technique in this package is XChaCha20-Poly1305 which is the extended nonce variant of the ChaCha20-Poly1305 technique used in IPsec, SSH and Wireguard.

The encryption method follows RFC 8439 ‘Authenticated Encryption with Additional Data (AEAD)’

• The nonce used within ‘monocypher’ is 24-bytes (192 bits). This is large enough that counter/ratcheting mechanisms do not need to be used, and random bytes are unlikely to generate the same nonce twice in any reasonable timeframe.
• The nonce is created internally using random bytes from the cryptographic random number generator from the system this is running on.
• In general when encrypting data using Authenticated Encryption:
  • Keep the following items secret:
    • the original data (obviously!)
    • the encryption key.
  • These items are not secret:
    • Nonce
    • MAC - message authentication code
    • Number of bytes of data

File structure

The data structure is a concatenation of the nonce, mac and encrypted data

• [nonce] [mac] [encrypted data]
  • [nonce] = 24 bytes
  • [mac] = 16 bytes
  • [encrypted data] = remaining bytes

Included Cryptographic Libraries

The package relies on the cryptographic algorithms supplied by monocypher