openssl_cipher_key_length reports the required parameter size for a named OpenSSL cipher.
The examples explain the data format, expected results and the difference between this API and nearby cryptographic operations.
What It Does
The operation is intended for: openssl_cipher_key_length reports the required parameter size for a named OpenSSL cipher.
The OpenSSL extension must be enabled.
Syntax and Return Value
openssl_cipher_key_length(string $cipher_algo): int|false| Parameter | Purpose |
|---|---|
| $cipher_algo (string) | Cipher algorithm choice; keep matched between encryption and decryption. |
The declared return type is shown above. Errors can include false results or exceptions depending on this API: Do not confuse key length and IV length; random IVs are not necessarily secret but may have strict uniqueness requirements.
Example 1: Basic Operation
GCM requires a 12-byte nonce and a 32-byte key for AES-256-GCM.
<?php
$length = openssl_cipher_key_length("aes-256-gcm");
var_dump($length);Example 2: A Different Use Case
Check that the cipher-specific IV or key size changes with the algorithm.
<?php
// Check the alternative case.
$length = openssl_cipher_key_length("aes-128-cbc");
var_dump($length);Practical Example: Checking the Result
Check that the cipher-specific IV or key size changes with the algorithm.
<?php
// Verify the expected behavior before using results.
$length = openssl_cipher_key_length("aes-256-ctr");
var_dump($length);Important Behavior and Edge Cases
Do not confuse key length and IV length; random IVs are not necessarily secret but may have strict uniqueness requirements.
Do not confuse key length and IV length; random IVs are not necessarily secret but may have strict uniqueness requirements.
Comparison with Related Functions
| Approach | Key distinction |
|---|---|
| openssl_cipher_key_length | openssl_cipher_key_length reports the required parameter size for a named OpenSSL cipher. |
| Related technique | Use the returned lengths to validate inputs before openssl_encrypt or openssl_decrypt. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Confusing this operation with a neighboring cryptographic or security mechanism | Use the returned lengths to validate inputs before openssl_encrypt or openssl_decrypt. |
| Ignoring a security prerequisite or failure case | Do not confuse key length and IV length; random IVs are not necessarily secret but may have strict uniqueness requirements. |
Key Takeaways
- openssl_cipher_key_length reports the required parameter size for a named OpenSSL cipher.
- Do not confuse key length and IV length; random IVs are not necessarily secret but may have strict uniqueness requirements.
- Use the returned lengths to validate inputs before openssl_encrypt or openssl_decrypt.
Apply this behavior to a real application only after confirming the required extension, configuration and failure handling on the deployment runtime.