/// <summary>
/// Makes sure that the stamp format is either 0 or 1, just in case we
/// start to support say validating another stamp format but not
/// producing it in the same ship.
/// </summary>
/// <param name="format">A StampFormat instance.</param>
private void ValidateStampFormat(StampFormat format)
{
if ((format != StampFormat.Version0) && (format != StampFormat.Version1))
{
throw new NotSupportedException("Only version 0 and version 1 stamps are supported.");
}
}
public void GenerateAFormatVersionZeroStampWithADenominationOfSeventeenAndEnsureItValidatesUsingTheHashcashReferenceImplementation()
{
Given("a resource of '*****@*****.**'", x => Resource = "foo123456789")
.And("an instance of the Minter class", x => Minter = new Minter())
.And("a denomination of sixteen", x => Denomination = 17)
.And("a stamp format version of 1", x => Format = StampFormat.Version0)
.When("the Mint method is called", x => Stamp = Minter.Mint(Resource, Denomination, Format))
.Then("it should generate a valid stamp", x => IsValidStamp(Denomination, Resource, Stamp, 0));
}
private static void Main(string[] args)
{
string resource = args[0];
int denomination = int.Parse(args[1]);
StampFormat format = (StampFormat)Enum.Parse(typeof(StampFormat), $"Version{args[2]}");
Minter minter = new Minter();
string stamp = minter.Mint(resource, denomination, DateTimeOffset.UtcNow, format);
Console.WriteLine(stamp);
Console.WriteLine("Press a key to exit...");
Console.ReadKey();
}
/// <summary>
/// Mints a stamp given the input parameters.
/// </summary>
/// <param name="resource">The resource that the stamp is to be minted for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A string representation of the hashcash stamp.</returns>
public string Mint(string resource, int requiredDenomination, DateTime date, StampFormat format)
{
this.ValidateResource(resource);
this.ValidateRequiredDenomination(requiredDenomination);
this.ValidateStampFormat(format);
int prefixLength;
byte[] blankStamp = this.CreateBlankStamp(resource, requiredDenomination, date, format, out prefixLength);
byte[] collisionStamp = this.ComputePartialCollisionStamp(blankStamp, requiredDenomination, format, prefixLength);
string stamp = Encoding.ASCII.GetString(collisionStamp);
return(stamp);
}
public static int Main(string[] args)
{
int returnCode = 0;
try
{
string resource = args[0];
int denomination = int.Parse(args[1]);
StampFormat format = (StampFormat)Enum.Parse(typeof(StampFormat), string.Format("Version{0}", args[2]));
NHashcash.Minter minter = new NHashcash.Minter();
string stamp = minter.Mint(resource, denomination, DateTime.Now, format);
Console.WriteLine(stamp);
}
catch (Exception ex)
{
Console.WriteLine(ex);
returnCode = 1;
}
return(returnCode);
}
/// <summary>
/// Mints a stamp given the input parameters.
/// </summary>
/// <param name="resource">The resource that the stamp is to be minted for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A string representation of the hashcash stamp.</returns>
public string Mint(string resource, int requiredDenomination, StampFormat format)
{
return(Mint(resource, requiredDenomination, DateTimeOffset.UtcNow, format));
}
/// <summary>
/// Mints a stamp given the input parameters.
/// </summary>
/// <param name="resource">The resource that the stamp is to be minted for.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A string representation of the hashcash stamp.</returns>
public string Mint(string resource, DateTimeOffset date, StampFormat format)
{
return(Mint(resource, DefaultDenomination, date, format));
}
/// <summary>
/// Generates the stamp prefix bytes from the inputs.
/// </summary>
/// <param name="resource">The resource that the stamp is being produced for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A byte array containing the stamp prefix.</returns>
private byte[] GenerateStampPrefixBytes(string resource, int requiredDenomination, DateTimeOffset date, StampFormat format)
{
string stampPrefix = null;
string stampDate = date.ToString("yymmdd");
switch (format)
{
case StampFormat.Version0:
stampPrefix = $"0:{stampDate}:{resource}:";
break;
case StampFormat.Version1:
stampPrefix = $"1:{requiredDenomination}:{stampDate}:{resource}::";
break;
}
byte[] stampPrefixBytes = Encoding.ASCII.GetBytes(stampPrefix);
return(stampPrefixBytes);
}
/// <summary>
/// Creates a byte array containing the stamp prefix and is padded out to the required length.
/// </summary>
/// <param name="resource">The resource that the stamp is being produced for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp.</param>
/// <param name="prefixLength">The length of the stamp prefix after all its elements have been pieced together.</param>
/// <returns>A byte array containing the stamp prefix and the required amount of padding.</returns>
private byte[] CreateBlankStamp(string resource, int requiredDenomination, DateTimeOffset date, StampFormat format, out int prefixLength)
{
byte[] stampPrefixBytes = GenerateStampPrefixBytes(resource, requiredDenomination, date, format);
prefixLength = stampPrefixBytes.Length;
int paddedLength = CalculatePaddedLength(prefixLength);
byte[] blankStamp = new byte[paddedLength];
Array.Copy(stampPrefixBytes, blankStamp, stampPrefixBytes.Length);
return(blankStamp);
}
/// <summary>
/// This is the main part of the algorithm. It takes a blank template stamp and randomly replaces the
/// characters after the prefix until
/// </summary>
/// <param name="blankStamp"></param>
/// <param name="requiredDenomination"></param>
/// <param name="format"></param>
/// <param name="prefixLength"></param>
/// <returns></returns>
private byte[] ComputePartialCollisionStamp(byte[] blankStamp, int requiredDenomination, StampFormat format, int prefixLength)
{
byte[] collisionStamp = blankStamp;
int randomRangeLowerLimit = prefixLength;
int randomRangeUpperLimit = collisionStamp.Length;
SHA1Managed provider = new SHA1Managed();
int hashCounter = 0;
bool collisionFound = false;
while (collisionFound == false)
{
if (format == StampFormat.Version1)
{
byte[] hashCounterBytes = CreateCounterBasedOnCharacterSet(hashCounter);
Array.Copy(
hashCounterBytes,
0,
collisionStamp,
collisionStamp.Length - hashCounterBytes.Length,
hashCounterBytes.Length
);
randomRangeUpperLimit = collisionStamp.Length - hashCounterBytes.Length - 1;
collisionStamp[randomRangeUpperLimit] = 58;
}
int bytePosition = _numberGenerator.Next(randomRangeLowerLimit, randomRangeUpperLimit);
byte characterByte = GetRandomCharacter();
collisionStamp[bytePosition] = characterByte;
byte[] collisionStampHash = provider.ComputeHash(collisionStamp);
collisionFound = IsCollisionOfRequiredDenomination(collisionStampHash, requiredDenomination);
hashCounter++;
}
return(collisionStamp);
}
/// <summary>
/// Mints a stamp given the input parameters.
/// </summary>
/// <param name="resource">The resource that the stamp is to be minted for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A string representation of the hashcash stamp.</returns>
public string Mint(string resource, int requiredDenomination, StampFormat format)
{
return(this.Mint(resource, requiredDenomination, DateTime.Now, format));
}
/// <summary>
/// Mints a stamp given the input parameters.
/// </summary>
/// <param name="resource">The resource that the stamp is to be minted for.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A string representation of the hashcash stamp.</returns>
public string Mint(string resource, DateTime date, StampFormat format)
{
return(this.Mint(resource, this.DefaultDenomination, date, format));
}
/// <summary>
/// Generates the stamp prefix bytes from the inputs.
/// </summary>
/// <param name="resource">The resource that the stamp is being produced for.</param>
/// <param name="requiredDenomination">The required denomination of the stamp.</param>
/// <param name="date">The date that the stamp is to be minted for.</param>
/// <param name="format">The format of the stamp to be produced.</param>
/// <returns>A byte array containing the stamp prefix.</returns>
private byte[] GenerateStampPrefixBytes(string resource, int requiredDenomination, DateTime date, StampFormat format)
{
string stampPrefix = null;
string stampDate = date.ToString("yyMMdd");
switch (format)
{
case StampFormat.Version0:
stampPrefix = string.Format(
"0:{0}:{1}:",
stampDate,
resource
);
break;
case StampFormat.Version1:
stampPrefix = string.Format(
"1:{0}:{1}:{2}::",
requiredDenomination,
stampDate,
resource
);
break;
}
byte[] stampPrefixBytes = Encoding.ASCII.GetBytes(stampPrefix);
return(stampPrefixBytes);
}
