libsodium_crypto_core_hchacha20 (libsodium v3.0.1)

The HChaCha20 core function, which derives a outputbytes/0 byte subkey from a keybytes/0 byte key and a inputbytes/0 byte input (typically the first 16 bytes of an extended nonce). It is the building block of XChaCha20.

The constbytes/0 byte constant C is normally the 16-byte string <<"expand 32-byte k">>. This is a low-level primitive: it is not a general-purpose key derivation function, and the key must be secret and uniformly random.

Key = libsodium_randombytes:buf(libsodium_crypto_core_hchacha20:keybytes()),
In = libsodium_randombytes:buf(libsodium_crypto_core_hchacha20:inputbytes()),
Out = libsodium_crypto_core_hchacha20:crypto_core_hchacha20(In, Key, <<"expand 32-byte k">>),
32 = byte_size(Out),
Out = libsodium_crypto_core_hchacha20:crypto_core_hchacha20(In, Key, <<"expand 32-byte k">>).

Summary

Types

c()

A crypto_core_hchacha20_CONSTBYTES (16-byte) binary.

in()

A crypto_core_hchacha20_INPUTBYTES (16-byte) binary.

k()

A crypto_core_hchacha20_KEYBYTES (32-byte) binary.

out()

A crypto_core_hchacha20_OUTPUTBYTES (32-byte) binary.

Functions

constbytes()

Return crypto_core_hchacha20_constbytes(), in bytes.

crypto_core_hchacha20(In, K, C)

Compute the HChaCha20 core of the inputbytes/0 byte input In with the keybytes/0 byte key K and the constbytes/0 byte constant C, returning outputbytes/0 bytes.

inputbytes()

Return crypto_core_hchacha20_inputbytes(), in bytes.

keybytes()

Return crypto_core_hchacha20_keybytes(), in bytes.

outputbytes()

Return crypto_core_hchacha20_outputbytes(), in bytes.