private bool TryGenerateNumber(int offset, out int number, long?value = null)
{
number = 0;
var bufflen = 8 + this.Settings.Additional.Length;
Span <byte> challenge = stackalloc byte[bufflen];
if (value == null)
{
if (!this.Settings.TryGetChallengeInput(challenge, out bufflen, offset))
{
return(false);
}
}
else
{
if (!this.Settings.TryGetChallengeInput(value.Value, challenge, out bufflen))
{
return(false);
}
}
using var hmac = HmacProviderSelector.FromId(this.Settings.Algorithm);
Span <byte> buff = stackalloc byte[hmac.OutputSize];
if (!hmac.TryCompute(this.Settings.Secret.AsSpan(), challenge, buff, out bufflen))
{
return(false);
}
var transformer = CodeTransformerSelector.FromId(CodeTransformer.Rfc4226);
if (!transformer.TryTransform(buff.Slice(0, bufflen), out number))
{
return(false);
}
return(true);
}
private int GenerateNumber(int offset = 0, long?value = null)
{
var bufflen = 8 + this.Settings.Additional.Length;
Span <byte> challenge = stackalloc byte[bufflen];
if (value == null)
{
if (!this.Settings.TryGetChallengeInput(challenge, out bufflen, offset))
{
throw new Exception("Failed to generate challenge.");
}
}
else
{
if (!this.Settings.TryGetChallengeInput(value.Value, challenge, out bufflen))
{
throw new Exception("Failed to generate challenge.");
}
}
using var hmac = HmacProviderSelector.FromId(this.Settings.Algorithm);
Span <byte> buff = stackalloc byte[hmac.OutputSize];
if (!hmac.TryCompute(this.Settings.Secret.AsSpan(), challenge, buff, out bufflen))
{
throw new Exception("Failed to compute HMAC.");
}
var transformer = CodeTransformerSelector.FromId(CodeTransformer.Rfc4226);
if (!transformer.TryTransform(buff.Slice(0, bufflen), out var number))
{
throw new Exception("Failed to transform HMAC.");
}
return(number);
}