module chacha20

Note:

This repo has been archived, Its has been merged to experimental module inside vlib/x/crypto/chacha,20. Development will be carried out there.

chacha20

Chacha20 (and XChacha20) stream cipher encryption algorithm in V language based on RFC 8439.

Note that ChaCha20, like all stream ciphers, is not authenticated and allows attackers to silently tamper with the plaintext. For this reason, it is more appropriate as a building block than as a standalone encryption mechanism. Instead, consider using secure modules, like chacha20poly1305.

Contents

• Constants
• encrypt
• encrypt_with_counter
• new_cipher
• Cipher
  • free
  • reset
  • set_counter
  • encrypt
  • decrypt
  • xor_key_stream
  • rekey

Constants

const key_size = 32

size of ChaCha20 key, ie 256 bits size, in bytes

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const nonce_size = 12

size of ietf ChaCha20 nonce, ie 96 bits size, in bytes

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const x_nonce_size = 24

size of extended ChaCha20 nonce, called XChaCha20, 192 bits

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encrypt

fn encrypt(key []u8, nonce []u8, plaintext []u8) ![]u8

encrypt was a thin wrapper around two supported nonce size, ChaCha20 with 96 bits and XChaCha20 with 192 bits nonce. If you want more control with internal counter see encrypt_with_counter

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encrypt_with_counter

fn encrypt_with_counter(key []u8, nonce []u8, ctr u32, plaintext []u8) ![]u8

encrypt_with_counter encrypts plaintext with internal counter set to ctr

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new_cipher

fn new_cipher(key []u8, nonce []u8) !&Cipher

new_cipher creates a new ChaCha20 stream cipher with the given 32 bytes key and a 12 or 24 bytes nonce. If a nonce of 24 bytes is provided, the XChaCha20 construction will be used. It returns an error if key or nonce have any other length.

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Cipher

free

fn (mut c Cipher) free()

free the resources taken by the Cipher c. Dont use cipher after .free call

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reset

fn (mut c Cipher) reset()

reset quickly sets all Cipher's fields to default value

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set_counter

fn (mut c Cipher) set_counter(ctr u32)

set_counter sets Cipher's counter

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encrypt

fn (mut c Cipher) encrypt(mut dst []u8, src []u8)

encrypt encrypts plaintext in src bytes and stores ciphertext result in dst. Its fullfills cipher.Block.encrypt interface.

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decrypt

fn (mut c Cipher) decrypt(mut dst []u8, src []u8)

decrypt does reverse of .encrypt() operation, decrypts ciphertext in src, and stores the result in dst. decrypt fullfills cipher.Block.decrypt interface.

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xor_key_stream

fn (mut c Cipher) xor_key_stream(mut dst []u8, src []u8)

xor_key_stream xors each byte in the given slice in the src with a byte from the cipher's key stream. It fullfills cipher.Stream interface. Its does encrypts plaintext message in src and stores ciphertext result in dst in single shot of run of encryption.

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rekey

fn (mut c Cipher) rekey(key []u8, nonce []u8) !

rekey resets internal Cipher's state and reinitializes state with the provided key and nonce

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