Poly1305 Component

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The Poly1305 component may be used to produce a MAC (or Tag) value using the Poly1305 algorithm.

Syntax

TipcPoly1305

Remarks

The Poly1305 component implements the Poly1305 algorithm defined in RFC 7539. This may be used to compute a MAC (or Tag) value on data of any length.

The Key must be set to a 256 bit (32 byte) key before computing the MAC. The computed MAC is 128 bit (32 bytes) in size.

ComputeMAC Notes

ComputeMAC computes the MAC (Message Authentication Code) from the input data.

Before calling this method set Key to a 256 bit (32 byte) key. If EncodeMAC is set to True (default) the output data will be hex encoded.

Input Notes

The component will determine the source of the input based on which properties are set.

The order in which the input properties are checked are as follows:

• InputFile
• InputMessage

After calling this method MACValue will be populated with the computed 128 bit (16 byte) value.

ComputeMAC Example

Poly1305 poly1305 = new Poly1305();
poly1305.KeyB = new byte[] { 0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a, 0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0, 0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09, 0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0 };
poly1305.InputMessage = "Hello Polly";
poly1305.EncodeMAC = true; //hex output
poly1305.ComputeMAC();

//This outputs "113019A3ACF5ED2FBB7A45AC1FD67DA1"
Console.WriteLine(poly1305.MACValue);

ComputeMACBlock Notes

ComputeMACBlock allows input to the component to be specified in blocks. This method will return the MAC value only when the parameter LastBlock is True.

InputBuffer specifies the input data.

LastBlock specifies whether the block is the last block. If this is False the method will return an empty byte array.

To calculate the MAC value of data that is broken apart into multiple blocks make multiple calls to this method. For instance:

//Encode output in hex
poly1305.EncodeMAC = true; //hex output

//Pass any number of parts, of any size
poly1305.ComputeMACBlock(part1,false);
poly1305.ComputeMACBlock(part2,false);
poly1305.ComputeMACBlock(part3,false);

//Pass true for the last block
poly1305.ComputeMACBlock(lastPart,true);

//The MACValue property holds the MAC value
Console.WriteLine(poly1305.MACValue);