protected override void RestoreSymmertricKey(byte[] sharedSecretBytes)
{
byte[] merchantIdentifier = GetHashSha256Bytes(parameters.MerchantIdentifier);
ConcatenationKdfGenerator generator = new ConcatenationKdfGenerator(new Sha256Digest());
byte[] algorithmIdBytes = Encoding.UTF8.GetBytes((char)0x0d + "id-aes256-GCM");
byte[] partyUInfoBytes = Encoding.UTF8.GetBytes("Apple");
byte[] partyVInfoBytes = merchantIdentifier;
byte[] otherInfoBytes = Combine(Combine(algorithmIdBytes, partyUInfoBytes), partyVInfoBytes);
generator.Init(new KdfParameters(sharedSecretBytes, otherInfoBytes));
EncryptionKeyBytes = new byte[32];
generator.GenerateBytes(EncryptionKeyBytes, 0, EncryptionKeyBytes.Length);
}
static byte[] DeriveKey(IDictionary <string, object> header, int cekSizeBits, ECPublicKeyParameters externalPublicKey,
ECPrivateKeyParameters ephemeralPrvKey)
{
var z = EcdhKeyAgreementZ(externalPublicKey, ephemeralPrvKey);
var kdfGen = new ConcatenationKdfGenerator(new Sha256Digest());
byte[] algId = Encoding.ASCII.GetBytes(header["enc"].ToString());
byte[] apu = header.ContainsKey("apu") ? Base64Url.Decode((string)header["apu"]) : Arrays.Empty;
byte[] apv = header.ContainsKey("apv") ? Base64Url.Decode((string)header["apv"]) : Arrays.Empty;
byte[] kdl = CalcBeLengthArray(cekSizeBits);
var otherInfo = Arrays.Concat(PrependLength(algId), PrependLength(apu), PrependLength(apv), kdl);
//Console.Out.WriteLine($"otherInfo={VAU.ByteArrayToHexString(otherInfo)}");
kdfGen.Init(new KdfParameters(z, otherInfo));
byte[] secretKeyBytes = new byte[32];
kdfGen.GenerateBytes(secretKeyBytes, 0, secretKeyBytes.Length);
return(secretKeyBytes);
}
public IKdfCalculator <AgreementKdfParameters> From(byte[] shared)
{
AgreementKdfParameters parameters = new AgreementKdfParameters(new FipsKdfAlgorithm(algorithm, prf), shared, iv);
if (parameters.Algorithm.Kdf == X963.Algorithm)
{
IDerivationFunction df = new Kdf2BytesGenerator(FipsShs.CreateDigest((FipsDigestAlgorithm)parameters.Prf.BaseAlgorithm));
df.Init(new KdfParameters(parameters.GetShared(), parameters.GetIV()));
return(new AgreementKdfCalculator(parameters, df));
}
else
{
IDerivationFunction df = new ConcatenationKdfGenerator(FipsShs.CreateDigest((FipsDigestAlgorithm)parameters.Prf.BaseAlgorithm));
df.Init(new KdfParameters(parameters.GetShared(), parameters.GetIV()));
return(new AgreementKdfCalculator(parameters, df));
}
}
