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sodium_crypto_generichash_update	sodium_crypto_kdf_keygen

Sodium Functions	Last updated: Mon, 26 Oct 2026

sodium_crypto_kdf_derive_from_key

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_kdf_derive_from_key — Derive a subkey

Description

function sodium_crypto_kdf_derive_from_key(
    int $subkey_length,
    int $subkey_id,
    string $context,
    #[\SensitiveParameter] string $key
): string

Derive a subkey from a root key and additional context.

Similar to hash_hkdf().

Parameters

subkey_length: Length of the key to return (in bytes)
subkey_id: Return the Nth subkey from a given root key. Useful for seeking.
context: Application-specific context.
key: The root key from which the subkey is derived.

Return Values

A string of pseudorandom (raw binary) bytes.

sodium_crypto_generichash_update	sodium_crypto_kdf_keygen

Sodium Functions	Last updated: Mon, 26 Oct 2026