libraryDocs / crypto / chacha20

crypto.chacha20

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ChaCha20 stream cipher library, the IETF variant with a 96-bit nonce and a 32-bit block counter.

Encryption and decryption are the same operation, the data is XORed with the keystream.

A key and nonce pair must never be used twice, otherwise both plaintexts can be recovered. If nonces are random, prefer crypto.xchacha20, its 192-bit nonce is safe to generate randomly.

ChaCha20 alone does not authenticate the data, use a MAC ( e.g. crypto.hmac ) over the ciphertext to detect tampering.

See RFC 8439 for the algorithm.

Fields

Name	Type	Description
`key_size`	`integer`	= `32`
`nonce_size`	`integer`	= `12`
`block_size`	`integer`	= `64`

Functions

`crypto.chacha20.block`	Computes a single 64-byte ChaCha20 keystream block.
`crypto.chacha20.encrypt`	Encrypts or decrypts the data with ChaCha20.

#crypto.chacha20.block

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function crypto.chacha20.block(key: string, nonce: string, counter?: integer): string

Computes a single 64-byte ChaCha20 keystream block.

Parameters

Name	Type	Description
`key`	`string`	The 32-byte key.
`nonce`	`string`	The 12-byte nonce.
`counter`optional	`integer`	The block counter, default is `0`.

Returns

Type	Name	Description
`string`	`block`	The 64-byte keystream block.

#crypto.chacha20.encrypt

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function crypto.chacha20.encrypt(data: string, key: string, nonce: string, counter?: integer): string

Encrypts or decrypts the data with ChaCha20.

The data can be processed in parts: each part except the last must be a multiple of 64 bytes long, and counter of the next part is counter + #part / 64.

Parameters

Name	Type	Description
`data`	`string`	The plaintext to encrypt or the ciphertext to decrypt.
`key`	`string`	The 32-byte key.
`nonce`	`string`	The 12-byte nonce.
`counter`optional	`integer`	The initial block counter, default is `0`.

Returns

Type	Name	Description
`string`	`result`	The ciphertext or plaintext, same length as `data`.