/**
* This method creates a new random byte buffer from which a new scratch code is generated. This
* function is invoked if a scratch code generated from the main buffer is invalid because it does
* not satisfy the scratch code restrictions.
*
* @return A valid scratch code.
*/
private int generateScratchCode() {
while (true) {
byte[] scratchCodeBuffer = new byte[BYTES_PER_SCRATCH_CODE];
secureRandom.nextBytes(scratchCodeBuffer);
int scratchCode = calculateScratchCode(scratchCodeBuffer);
if (scratchCode != SCRATCH_CODE_INVALID) {
return scratchCode;
}
}
}
@Override
public GoogleAuthenticatorKey createCredentials() {
// Allocating a buffer sufficiently large to hold the bytes required by
// the secret key and the scratch codes.
byte[] buffer = new byte[SECRET_BITS / 8 + SCRATCH_CODES * BYTES_PER_SCRATCH_CODE];
secureRandom.nextBytes(buffer);
// Extracting the bytes making up the secret key.
byte[] secretKey = Arrays.copyOf(buffer, SECRET_BITS / 8);
String generatedKey = calculateSecretKey(secretKey);
// Generating the verification code at time = 0.
int validationCode = calculateValidationCode(secretKey); // == calculateCode(secretKey, 0)
// Calculate scratch codes
List<Integer> scratchCodes = calculateScratchCodes(buffer);
// List<Integer> scratchCodes = null;
// System.out.println(generatedKey);
// System.out.println(validationCode);
return new GoogleAuthenticatorKey(generatedKey, validationCode, scratchCodes);
}