libraryDocs / crypto / xchacha20

crypto.xchacha20

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XChaCha20 stream cipher library, ChaCha20 with a 192-bit nonce.

The nonce is large enough to be generated randomly for every message.

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

XChaCha20 alone does not authenticate the data, use a MAC ( e.g. crypto.hmac ) over the ciphertext to detect tampering.

See draft-irtf-cfrg-xchacha for the algorithm.

Fields

Name	Type	Description
`key_size`	`integer`	= `32`
`nonce_size`	`integer`	= `24`
`block_size`	`integer`	= `64`

Functions

`crypto.xchacha20.encrypt`	Encrypts or decrypts the data with XChaCha20.
`crypto.xchacha20.hchacha20`	Derives a 32-byte subkey from the key and a 16-byte nonce with HChaCha20.

#crypto.xchacha20.encrypt

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function crypto.xchacha20.encrypt(data: string, key: string, nonce: string, counter?: integer): string

Encrypts or decrypts the data with XChaCha20.

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 24-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`.

#crypto.xchacha20.hchacha20

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function crypto.xchacha20.hchacha20(key: string, nonce: string): string

Derives a 32-byte subkey from the key and a 16-byte nonce with HChaCha20.

Parameters

Name	Type	Description
`key`	`string`	The 32-byte key.
`nonce`	`string`	The 16-byte nonce.

Returns

Type	Name	Description
`string`	`subkey`	The 32-byte subkey.