org.cryptacular.generator

Class AbstractOTPGenerator

java.lang.Object

org.cryptacular.generator.AbstractOTPGenerator

Direct Known Subclasses:

HOTPGenerator, TOTPGenerator

public abstract class AbstractOTPGenerator
extends java.lang.Object

Abstract base class for HOTP and TOTP OTP generation schemes.

Field Summary

Fields

Modifier and Type	Field and Description
private static int[]	MODULUS Array of modulus values indexed per number of digits in OTP output.
private int	numberOfDigits Number of digits in generated OTP.

Constructor Summary

Constructors

Constructor and Description
AbstractOTPGenerator()

Method Summary

Modifier and Type	Method and Description
protected int	generateInternal(byte[] key, long count) Internal OTP generation method.
protected abstract org.bouncycastle.crypto.Digest	getDigest()
int	getNumberOfDigits()
void	setNumberOfDigits(int digits) Sets the numbers in the generated OTP.
private int	truncate(byte[] hmac) Truncates HMAC output onto an unsigned (i.e.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MODULUS

private static final int[] MODULUS

Array of modulus values indexed per number of digits in OTP output.

numberOfDigits

private int numberOfDigits

Number of digits in generated OTP.

Constructor Detail

AbstractOTPGenerator

public AbstractOTPGenerator()

Method Detail

getNumberOfDigits

public int getNumberOfDigits()

Returns:

Number of digits in generated OTP.

setNumberOfDigits

public void setNumberOfDigits(int digits)

Sets the numbers in the generated OTP.

Parameters:

digits - Number of digits in generated OTP. MUST be in the range 6 - 9. Default is 6.

generateInternal

protected int generateInternal(byte[] key,
                               long count)

Internal OTP generation method.

Parameters:

key - Per-user key.

count - Counter moving factor.

Returns:

Integer OTP.

getDigest

protected abstract org.bouncycastle.crypto.Digest getDigest()

Returns:

Digest algorithm used for HMAC operation.

truncate

private int truncate(byte[] hmac)

Truncates HMAC output onto an unsigned (i.e. 31-bit) integer.

Parameters:

hmac - HMAC output.

Returns:

Truncated output.