Known salt (B64): Tb9oj07UhwU= (8)
Known key (B64): MII0yj+MC0mHNx254Voar80bi9P7jmocs0+x+inaxBE=
Known iv (B64): l/PvkDjOKMFZe73KptrvWw== (16)
Shared Key (B64): ql8zvN03p6kroSwNrcKbxk4zSBQFkgQZEumvqVIDMAE=
** DECRYPT **
Encrypted Message: ...
Decoded Salt (B64): Tb9oj07UhwU= (8)
PBKDF2 KEY (B64): MII0yj+MC0mHNx254Voar80bi9P7jmocs0+x+inaxBE=
iv (B64): JanbU1jI30lb6yfjq/adjA== (16)
Decrypted Message: 

# https://www.php.net/manual/en/function.openssl-pbkdf2.php
    $password = $sharedKey;
    $salt = openssl_random_pseudo_bytes(16);  # What's the salt length ?
    $keyLength = 20;  # What's the key length here ?
    $iterations = 100000;
    $generatedKey = openssl_pbkdf2($password, $salt, $keyLength, $iterations, 'sha256');
    echo bin2hex($generatedKey)."\n";
    echo base64_encode($generatedKey)."\n";

    $iv = openssl_random_pseudo_bytes(16); // AES-256-CBC requires 16-byte IV
    $cipherText = openssl_encrypt($message, 'aes-256-cbc', $generatedKey, OPENSSL_RAW_DATA, $iv);
    return base64_encode($iv . $cipherText);