/// <inheritdoc />
protected override void InitState(byte[] key)
{
// Prepend the supplied IV with zeros (as per FIPS PUB 81)
byte[] workingIv = new byte[CipherBlockSize];
IV.CopyBytes_NoChecks(0, workingIv, CipherBlockSize - IV.Length, IV.Length);
Array.Clear(workingIv, 0, CipherBlockSize - IV.Length);
IV = workingIv;
Reset();
BlockCipher.Init(true, key); // Streaming mode - cipher always used in encryption mode
}