ChaCha20 Python wrapper

ChaCha20 and ChaCha20-Poly1305 encryption and decryption can be tested with Python wrappers.

To get a template using the CLI, run:

crypto-condor-cli get-wrapper ChaCha20 --language Python

There is a practical example with PyCryptodome:

crypto-condor-cli get-wrapper ChaCha20 --language Python --example 1

Encrypt

To test an implementation of ChaCha20 encryption, the function must:

  • follow the naming convention;

  • implement the Encrypt protocol.

Naming convention

CC_ChaCha20_encrypt

Protocol

protocol crypto_condor.primitives.ChaCha20.Encrypt

Represents a function that encrypts with ChaCha20.

Classes that implement this protocol must have the following methods / attributes:

__call__(key, pt, nonce, init_counter=0)

Encrypts with ChaCha20.

Parameters:

  • key (bytes) – The symmetric key.

  • pt (bytes) – The plaintext to encrypt.

  • nonce (bytes) – The nonce.

  • init_counter (int) – A position to seek in the keystream before encrypting, in bytes.

Returns:

The ciphertext.

Return type:

bytes

Decrypt

To test an implementation of ChaCha20 decryption, the function must:

  • follow the naming convention;

  • implement the Decrypt protocol.

Naming convention

CC_ChaCha20_encrypt

Protocol

protocol crypto_condor.primitives.ChaCha20.Decrypt

Represents a function that decrypts with ChaCha20.

Classes that implement this protocol must have the following methods / attributes:

__call__(key, ct, nonce, init_counter=0)

Decrypts with ChaCha20.

Parameters:

  • key (bytes) – The symmetric key.

  • ct (bytes) – The ciphertext to decrypt.

  • nonce (bytes) – The nonce.

Keyword Arguments:

init_counter – A position to seek in the keystream before encrypting, in bytes.

Returns:

The plaintext.

Return type:

bytes

Encrypt with Poly1305

To test an implementation of ChaCha20-Poly1305 authenticated encryption, the function must:

  • follow the naming convention;

  • implement the EncryptPoly protocol.

Naming convention

CC_ChaCha20_encrypt_poly

Protocol

protocol crypto_condor.primitives.ChaCha20.EncryptPoly

Represents a function that encrypts with ChaCha20-Poly1305.

Classes that implement this protocol must have the following methods / attributes:

__call__(key, pt, nonce, aad)

Encrypts with ChaCha20-Poly1305.

Parameters:

  • key (bytes) – The symmetric key.

  • pt (bytes) – The plaintext to encrypt.

  • nonce (bytes) – The nonce.

  • aad (bytes) – The associated data.

Returns:

A tuple containing the ciphertext and the MAC tag.

Raises:

ValueError – If an input is incorrect (e.g. the nonce size is invalid).

Return type:

tuple[bytes, bytes]

Decrypt

To test an implementation of ChaCha20-Poly1305 authenticated decryption, the function must:

  • follow the naming convention;

  • implement the DecryptPoly protocol.

Naming convention

CC_ChaCha20_decrypt_poly

Protocol

protocol crypto_condor.primitives.ChaCha20.DecryptPoly

Represents a function that decrypts with ChaCha20-Poly1305.

Classes that implement this protocol must have the following methods / attributes:

__call__(key, ct, nonce, tag, aad)

Decrypts with ChaCha20-Poly1305.

Parameters:

  • key (bytes) – The symmetric key.

  • ct (bytes) – The ciphertext to decrypt.

  • nonce (bytes) – The 12-byte nonce.

  • tag (bytes) – The MAC tag.

  • aad (bytes) – The associated data.

Returns:

The decrypted plaintext.

Raises:

ValueError – If an input is incorrect (e.g. the nonce size is not 12 bytes) or if the MAC verification failed.

Return type:

bytes | None