/// <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>暗号化</summary>
/// <param name="plaint">平文（plaintext）</param>
/// <returns>AEAD実行結果オブジェクト</returns>
public override void Encrypt(byte[] plaint)
{
// 初期化
this.InitAesCbc(true);
// CCM操作の実行
byte[] ciphert = new byte[this._aesCBC.GetOutputSize(plaint.Length)];
int len = this._aesCBC.ProcessBytes(plaint, 0, plaint.Length, ciphert, 0);
len += this._aesCBC.DoFinal(ciphert, len);
// 認証タグ（MAC）を取得
// Concatenate the [AAD], the [IV], the [ciphertext], and the [AL value].
byte[] temp = ArrayOperator.CombineArray(this.AAD, this.IV);
temp = ArrayOperator.CombineArray(temp, ciphert);
temp = ArrayOperator.CombineArray(temp, this.AL);
byte[] tag = this._hmac.ComputeHash(temp);
Array.Resize(ref tag, TAG_LEN);
// 結果を返す
this._result = new AeadResult()
{
Aead = ArrayOperator.CombineArray(ciphert, tag),
Ciphert = ciphert,
Tag = tag,
};
}
/// <summary>暗号文と認証タグ（MAC）を結合</summary>
/// <returns>ciphert + tag</returns>
public byte[] CombineByteArrayForDecrypt()
{
return(ArrayOperator.CombineArray <byte>(this.Ciphert, this.Tag));
}
