/// <summary>復号化</summary>
/// <param name="input">AeadResult</param>
/// <returns>平文（plaintext）</returns>
public override byte[] Decrypt(AeadResult input)
{
// 初期化
this.InitAesCbc(false);
//認証タグ（MAC）を取得
// Concatenate the [AAD], the [Initialization Vector], the [ciphertext], and the [AL value].
byte[] temp = ArrayOperator.CombineArray(this.AAD, this.IV);
temp = ArrayOperator.CombineArray(temp, input.Ciphert);
temp = ArrayOperator.CombineArray(temp, this.AL);
byte[] tag = this._hmac.ComputeHash(temp);
Array.Resize(ref tag, TAG_LEN);
// タグの確認
if (!tag.SequenceEqual(input.Tag))
{
return(null);
}
// CCM操作の実行
byte[] plaint = new byte[this._aesCBC.GetOutputSize(input.Ciphert.Length)];
int len = this._aesCBC.ProcessBytes(input.Ciphert, 0, input.Ciphert.Length, plaint, 0);
len += this._aesCBC.DoFinal(plaint, len);
Array.Resize(ref plaint, len);
// 平文を返す。
return(plaint);
}
/// <summary>復号化</summary>
/// <param name="input">AeadResult</param>
/// <returns>平文（plaintext）</returns>
public override byte[] Decrypt(AeadResult input)
{
// AesGcm実装を初期化
this.InitAesGcm(false);
// aead = ciphert + tag
byte[] aead = null;
if (input.Aead == null)
{
aead = input.CombineByteArrayForDecrypt();
}
else
{
aead = input.Aead;
}
// GCM操作の実行
byte[] plaint = new byte[this._aesGcm.GetOutputSize(aead.Length)];
int len = this._aesGcm.ProcessBytes(aead, 0, aead.Length, plaint, 0);
len += this._aesGcm.DoFinal(plaint, len);
// 平文を返す。
return(plaint);
}
