PHP sodium_crypto_secretstream_xchacha20poly1305_pull() Function: Usage and Examples

In PHP, sodium_crypto_secretstream_xchacha20poly1305_pull() is useful when your application needs a specific operation rather than manually reproducing it. Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext.

Security context: The examples show API usage, not a complete secure messaging protocol. Keep encryption keys secret and use authenticated encryption when integrity is required.

Stream functions work with PHP stream resources, wrappers, contexts or custom filters. Not every wrapper supports every operation.

What Is sodium_crypto_secretstream_xchacha20poly1305_pull() in PHP?

Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext.

Signature:

sodium_crypto_secretstream_xchacha20poly1305_pull(string $state, string $ciphertext, string $additional_data = ''): array|false

Parameters:

• $state — Mutable crypto state returned by the corresponding initialization function.
• $ciphertext — Encrypted bytes produced by the matching encryption operation.
• $additional_data — Authenticated associated data that remains unencrypted.

Return value: array|false.

Example 1: Basic Usage

This first example shows the method or function in a minimal context. For environment-dependent operations, adapt the required path, stream or connection before running it.

<?php

$key = sodium_crypto_secretstream_xchacha20poly1305_keygen();
[$pushState, $header] = sodium_crypto_secretstream_xchacha20poly1305_init_push($key);
$encrypted = sodium_crypto_secretstream_xchacha20poly1305_push($pushState, "Report", "", SODIUM_CRYPTO_SECRETSTREAM_XCHACHA20POLY1305_TAG_FINAL);
$pullState = sodium_crypto_secretstream_xchacha20poly1305_init_pull($header, $key);
$decoded = sodium_crypto_secretstream_xchacha20poly1305_pull($pullState, $encrypted);
var_dump($decoded[0] === "Report");

The important operation is sodium_crypto_secretstream_xchacha20poly1305_pull(). Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state.

Example 2: Another Input or Scenario

The next example changes the input or surrounding context to show how the operation behaves in a second situation.

<?php

$key = sodium_crypto_secretstream_xchacha20poly1305_keygen();
[$pushState, $header] = sodium_crypto_secretstream_xchacha20poly1305_init_push($key);
$encrypted = sodium_crypto_secretstream_xchacha20poly1305_push($pushState, "Backup entry", "", SODIUM_CRYPTO_SECRETSTREAM_XCHACHA20POLY1305_TAG_FINAL);
$pullState = sodium_crypto_secretstream_xchacha20poly1305_init_pull($header, $key);
$decoded = sodium_crypto_secretstream_xchacha20poly1305_pull($pullState, $encrypted);
var_dump($decoded[0] === "Backup entry");

Compare the inputs and the handling of the return value with the first example. Avoid assuming that filesystem paths, resource states or binary bytes are interchangeable.

Practical Example: Applying the Operation

This example illustrates how the operation fits into a small application workflow. Paths, streams and secrets must be created or provided securely by the calling application.

<?php

$key = sodium_crypto_secretstream_xchacha20poly1305_keygen();
[$encryptionState, $header] = sodium_crypto_secretstream_xchacha20poly1305_init_push($key);
$parts = ["First line", "Second line"];
$cipherChunks = [];
foreach ($parts as $partIndex => $part) {
    $tag = $partIndex === count($parts) - 1 ? SODIUM_CRYPTO_SECRETSTREAM_XCHACHA20POLY1305_TAG_FINAL : SODIUM_CRYPTO_SECRETSTREAM_XCHACHA20POLY1305_TAG_MESSAGE;
    $cipherChunks[] = sodium_crypto_secretstream_xchacha20poly1305_push($encryptionState, $part, "", $tag);
}
$decryptionState = sodium_crypto_secretstream_xchacha20poly1305_init_pull($header, $key);
foreach ($cipherChunks as $cipherChunk) {
    $decoded = sodium_crypto_secretstream_xchacha20poly1305_pull($decryptionState, $cipherChunk);
    if ($decoded === false) { throw new RuntimeException("Authentication failed"); }
    echo $decoded[0], PHP_EOL;
}

Practical note: Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext.

Important Behavior and Edge Cases

• Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext.
• Check failure values and exceptions; do not assume every environment supports the same stream wrapper, extension or filesystem capability.
• When handling paths, streams or external input, validate inputs before using results and release resources after use.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• sodium_crypto_secretstream_xchacha20poly1305_pull() authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext.
• Use appropriate input types and verify results before continuing.
• Prefer specialized, safer APIs when the operation concerns untrusted input, encryption or network traffic.

In summary: Authenticates and decrypts one secretstream ciphertext chunk, advancing the stream state. A failed authentication is not recoverable plaintext. Build in error handling and use this function where its specific behavior matches the application requirements.