International PHP Conference Berlin 2023

sodium_crypto_stream_xchacha20_xor_ic

(PHP 8 >= 8.2.0)

sodium_crypto_stream_xchacha20_xor_icEncrypts a message using a nonce and a secret key (no authentication)

Descripción

sodium_crypto_stream_xchacha20_xor_ic(
    string $message,
    string $nonce,
    int $counter,
    string $key
): string

The function is similar to sodium_crypto_stream_xchacha20_xor() but adds the ability to set the initial value of the block counter to a non-zero value. This permits direct access to any block without having to compute the previous ones.

Precaución

This encryption is unauthenticated, and does not prevent chosen-ciphertext attacks. Make sure to combine the ciphertext with a Message Authentication Code, for example with sodium_crypto_aead_xchacha20poly1305_ietf_encrypt() function, or sodium_crypto_auth().

Parámetros

message

The message to encrypt.

nonce

24-byte nonce.

counter

The initial value of the block counter.

key

Key, possibly generated from sodium_crypto_stream_xchacha20_keygen().

Valores devueltos

Encrypted message, o false en caso de error.

Ejemplos

Ejemplo #1 sodium_crypto_stream_xchacha20_xor_ic() example

<?php
$n2 
random_bytes(SODIUM_CRYPTO_STREAM_XCHACHA20_NONCEBYTES);
$left  str_repeat("\x01"64);
$right str_repeat("\xfe"64);

// All at once:
$stream7_unified sodium_crypto_stream_xchacha20_xor($left $right$n2$key);

// Piecewise, with initial counter:
$stream7_left  sodium_crypto_stream_xchacha20_xor_ic($left$n20$key);
$stream7_right sodium_crypto_stream_xchacha20_xor_ic($right$n21$key);
$stream7_concat $stream7_left $stream7_right;

var_dump(strlen($stream7_concat));
var_dump($stream7_unified === $stream7_concat);
?>

El resultado del ejemplo sería algo similar a:

int(128)
bool(true)

Ver también

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