Expand description

AEAD XChaCha20Poly1305 as specified in the draft RFC.

Parameters:

  • secret_key: The secret key.
  • nonce: The nonce value.
  • ad: Additional data to authenticate (this is not encrypted and can be None).
  • ciphertext_with_tag: The encrypted data with the corresponding 16 byte Poly1305 tag appended to it.
  • plaintext: The data to be encrypted.
  • dst_out: Destination array that will hold the ciphertext_with_tag/plaintext after encryption/decryption.

ad: “A typical use for these data is to authenticate version numbers, timestamps or monotonically increasing counters in order to discard previous messages and prevent replay attacks.” See libsodium docs for more information.

dst_out: The output buffer may have a capacity greater than the input. If this is the case, only the first input length amount of bytes in dst_out are modified, while the rest remain untouched.

Errors:

An error will be returned if:

Panics:

A panic will occur if:

  • More than 2^32-1 * 64 bytes of data are processed.

Security:

  • It is critical for security that a given nonce is not re-used with a given key. Should this happen, the security of all data that has been encrypted with that given key is compromised.
  • Only a nonce for XChaCha20Poly1305 is big enough to be randomly generated using a CSPRNG. Nonce::generate() can be used for this.
  • To securely generate a strong key, use SecretKey::generate().
  • The length of the plaintext is not hidden, only its contents.

Example:

use orion::hazardous::aead;

let secret_key = aead::xchacha20poly1305::SecretKey::generate();
let nonce = aead::xchacha20poly1305::Nonce::generate();
let ad = "Additional data".as_bytes();
let message = "Data to protect".as_bytes();

// Length of the above message is 15 and then we accommodate 16 for the Poly1305
// tag.

let mut dst_out_ct = [0u8; 15 + 16];
let mut dst_out_pt = [0u8; 15];
// Encrypt and place ciphertext + tag in dst_out_ct
aead::xchacha20poly1305::seal(&secret_key, &nonce, message, Some(&ad), &mut dst_out_ct)?;
// Verify tag, if correct then decrypt and place message in dst_out_pt
aead::xchacha20poly1305::open(&secret_key, &nonce, &dst_out_ct, Some(&ad), &mut dst_out_pt)?;

assert_eq!(dst_out_pt.as_ref(), message.as_ref());

Re-exports

pub use crate::hazardous::stream::chacha20::SecretKey;
pub use crate::hazardous::stream::xchacha20::Nonce;

Functions

AEAD XChaCha20Poly1305 decryption as specified in the draft RFC.
AEAD XChaCha20Poly1305 encryption as specified in the draft RFC.