New returns a ChaCha20-Poly1305 AEAD that uses the given 256-bit key.

NewX returns a XChaCha20-Poly1305 AEAD that uses the given 256-bit key.

KeySize is the size of the key used by this AEAD, in bytes.

NonceSize is the size of the nonce used with the standard variant of this AEAD, in bytes.

NonceSizeX is the size of the nonce used with the XChaCha20-Poly1305 variant of this AEAD, in bytes.

Overhead is the size of the Poly1305 authentication tag, and the difference between a ciphertext length and its plaintext.