/// <summary>
/// Returns secret as a Base32 string with custom formatting.
/// It is up to the caller to secure given string.
/// </summary>
/// <param name="format">Format of Base32 string.</param>
public string GetBase32Secret(SecretFormatFlags format)
{
this.UnprotectSecret();
try {
return(ToBase32(this.SecretBuffer, this.SecretLength, format));
} finally {
this.ProtectSecret();
}
}
private static string ToBase32(byte[] bytes, int length, SecretFormatFlags format)
{
if (length == 0)
{
return(string.Empty);
}
var hasSpacing = (format & SecretFormatFlags.Spacing) == SecretFormatFlags.Spacing;
var hasPadding = (format & SecretFormatFlags.Padding) == SecretFormatFlags.Padding;
var isUpper = (format & SecretFormatFlags.Uppercase) == SecretFormatFlags.Uppercase;
var bitLength = (length * 8);
var textLength = bitLength / 5 + ((bitLength % 5) == 0 ? 0 : 1);
var totalLength = textLength;
var padLength = (textLength % 8 == 0) ? 0 : 8 - textLength % 8;
totalLength += (hasPadding ? padLength : 0);
var spaceLength = totalLength / 4 + ((totalLength % 4 == 0) ? -1 : 0);
totalLength += (hasSpacing ? spaceLength : 0);
var chars = new char[totalLength];
var index = 0;
var bits = 0;
var bitsRemaining = 0;
for (int i = 0; i < length; i++)
{
bits = (bits << 8) | bytes[i];
bitsRemaining += 8;
while (bitsRemaining >= 5)
{
var bitsIndex = (bits >> (bitsRemaining - 5)) & 0x1F;
bitsRemaining -= 5;
chars[index] = isUpper ? Base32Alphabet[bitsIndex] : char.ToLowerInvariant(Base32Alphabet[bitsIndex]);
index++;
if (hasSpacing && (index < chars.Length) && (bitsRemaining % 4 == 0))
{
chars[index] = ' ';
index++;
}
}
}
if (bitsRemaining > 0)
{
var bitsIndex = (bits & Base32Bitmask[bitsRemaining]) << (5 - bitsRemaining);
chars[index] = isUpper ? Base32Alphabet[bitsIndex] : char.ToLowerInvariant(Base32Alphabet[bitsIndex]);
index++;
}
if (hasPadding)
{
for (int i = 0; i < padLength; i++)
{
if (hasSpacing && (i % 4 == padLength % 4))
{
chars[index] = ' ';
index++;
}
chars[index] = '=';
index++;
}
}
return(new string(chars));
}
