CalculateResponse Method

This method calculates the response to the given challenge.

Syntax

[VB.NET]
Public Sub CalculateResponse()

[C#]
public void CalculateResponse();

Remarks

This method calculates Response to the given Challenge.

Before calling this method set OCRASuite to the suite obtained from the other party and set Challenge to the received challenge.

After setting OCRASuite the following properties are populated, which provide requirements for the response:

Inspect these properties to determine the requirements and provide any required values such as Counter or Password. Set Key to the key used during the HMAC computation. Set Challenge to the received challenge.

Call this method to calculate the response. After calling this method the Response property is populated. The response may then be transmitted to the other party for verification.

The following properties are applicable when calling this method:

Random Challenge Example

//First create the challenge on machine A
Ocra ocra = new Ocra();
ocra.ChallengeType = OcraChallengeTypes.ctRandom;
ocra.ChallengeLength = 10;
ocra.ChallengeFormat = OcraChallengeFormats.cfNumeric;
ocra.CreateChallenge();

string challenge = ocra.Challenge; //Value like "3891592139"
string ocraSuite = ocra.OCRASuite; //Value "OCRA-1:HOTP-SHA1-6:QN10"
//Send Challenge and OCRASuite to Machine B

//Upon receiving the challenge on Machine B, calculate a response
ocra = new Ocra();
ocra.OCRASuite = ocraSuite; //Received from other party
ocra.Challenge = challenge; //Received from other party
ocra.Key = "shared secret key";
ocra.CalculateResponse();

string response = ocra.Response; //Value like "574464"
//Send Response back to Machine A

//Upon receiving the response on Machine A, verify it
ocra = new Ocra();
ocra.OCRASuite = ocraSuite; //Original OCRASuite saved before sending the original challenge
ocra.Challenge = challenge; //Original challenge that was sent
ocra.Response = response;   //Received from other party
ocra.Key = "shared secret key";

bool isValid = ocra.VerifyResponse(); //Returns True if verified

Signature Challenge Example

//First create the challenge on machine A
Ocra ocra = new Ocra();
ocra.ChallengeType = OcraChallengeTypes.ctSignature;
ocra.ChallengeInput = "test input";
ocra.Key = "signature key";
ocra.ChallengeFormat = OcraChallengeFormats.cfHex;
ocra.CreateChallenge();

string challenge = ocra.Challenge; //Value like "973131F0"
string ocraSuite = ocra.OCRASuite; //Value "OCRA-1:HOTP-SHA1-6:QH08"
//Send Challenge and OCRASuite to Machine B

//Upon receiving the challenge on Machine B, calculate a response
ocra = new Ocra();
ocra.OCRASuite = ocraSuite; //Received from other party
ocra.Challenge = challenge; //Received from other party
ocra.Key = "shared secret key";
ocra.CalculateResponse();

string response = ocra.Response; //Value like "574464"
//Send Response back to Machine A

//Upon receiving the response on Machine A, verify it
ocra = new Ocra();
ocra.OCRASuite = ocraSuite; //Original OCRASuite saved before sending the original challenge
ocra.Challenge = challenge; //Original challenge that was sent
ocra.Response = response;   //Received from other party
ocra.Key = "shared secret key";

bool isValid = ocra.VerifyResponse(); //Returns True if verified

NOTE: This method has a corresponding asynchronous version (CalculateResponseAsync) for use in the WinRT environment.