private IFFX GetCipher(byte[] tweak, FfsConfigurationResponse ffs, FpeEncryptionKeyResponse encryptionKey, int radix)
{
IFFX cypher;
// set the tweak range and radix based on the FFS record
long twkmin = ffs.TweakMinLength.HasValue ? ffs.TweakMinLength.Value : 0;
long twkmax = ffs.TweakMaxLength.HasValue ? ffs.TweakMaxLength.Value : 0;
_fpe = ffs.EncryptionAlgorithm;
switch (_fpe.ToLower())
{
case FpeNameConstants.ff1:
cypher = new FF1(encryptionKey.UnwrappedDataKey, tweak, twkmin, twkmax, radix);
break;
case FpeNameConstants.ff3_1:
cypher = new FF3_1(encryptionKey.UnwrappedDataKey, tweak, radix);
break;
default:
throw new InvalidOperationException($"Unknown FPE Algorithm: {_fpe}");
}
return(cypher);
}
private int DecodeKeyNumIndex(FfsConfigurationResponse ffs, string str, int position)
{
if (position < 0)
{
// throw new InvalidOperationException($"Bad String decoding position for: {str}");
position = 0;
}
var charBuf = str.Substring(position, 1);
int encodedValue = ffs.OutputCharacters.IndexOf(charBuf);
return(encodedValue);
}
private FpeParseModel ParseInput(string input, FfsConfigurationResponse ffs, bool encrypt)
{
var inputRgxPattern = $"[{RegexEscape(ffs.InputCharacters)}]";
var firstCharacter = ffs.OutputCharacters.Substring(0, 1);
var invalidRgxPattern = $"[{RegexEscape(ffs.InputCharacters)}{RegexEscape(ffs.Passthrough)}]";
if (!encrypt)
{
inputRgxPattern = $"[{RegexEscape(ffs.OutputCharacters)}]";
firstCharacter = ffs.InputCharacters.Substring(0, 1);
invalidRgxPattern = $"[{RegexEscape(ffs.OutputCharacters)}{RegexEscape(ffs.Passthrough)}]";
}
var inputRgx = new Regex(inputRgxPattern);
var inputMatches = inputRgx.Matches(input);
var formattedPassthroughCharacters = Regex.Replace(input, inputRgxPattern, firstCharacter);
if (encrypt)
{
var invalidRgx = new Regex(invalidRgxPattern);
MatchCollection invalidMatch = invalidRgx.Matches(input);
if (invalidMatch.Count != input.Length)
{
throw new ArgumentOutOfRangeException("invalid character found in the input");
}
}
var inputSb = new StringBuilder();
foreach (Match group in inputMatches)
{
inputSb.Append(group.Value);
}
var result = new FpeParseModel
{
StringTemplate = formattedPassthroughCharacters,
Trimmed = inputSb.ToString(),
};
return(result);
}
private string EncodeKeyNum(FfsConfigurationResponse ffs, int keyNumber, string str, int position)
{
string buf;
if (position < 0)
{
throw new InvalidOperationException($"Bad String decoding position for: {str}");
}
var strChars = str.ToCharArray();
var charBuf = strChars[position];
var ct_value = ffs.OutputCharacters.IndexOf(charBuf);
var msb_encoding_bits = ffs.MsbEncodingBits;
ct_value = ct_value + (keyNumber << (int)msb_encoding_bits.Value);
var ch = ffs.OutputCharacters.Substring(ct_value, 1);
strChars[position] = ch.ToCharArray()[0];
buf = new string(strChars);
return(buf);
}
