Package com.bastiaanjansen.otp

Class OTPGenerator

java.lang.Object

com.bastiaanjansen.otp.OTPGenerator

Direct Known Subclasses:

HOTPGenerator, TOTPGenerator

public class OTPGenerator
extends Object

Generates one-time passwords

Author:

Bastiaan Jansen

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	OTPGenerator.Builder<B,G>	Abstract OTP builder

Field Summary

Fields

Modifier and Type	Field	Description
protected HMACAlgorithm	algorithm	Hashing algorithm used to generate code, defaults to SHA1
protected int	passwordLength	Number of digits for generated code in range 6...8, defaults to 6
protected byte[]	secret	Secret key used to generate the code, this should be a base32 string

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	OTPGenerator(int passwordLength, HMACAlgorithm algorithm, byte[] secret)	Constructs the generator with custom password length and hashing algorithm

Method Summary

Modifier and Type	Method	Description
protected String	generateCode(long counter)	Generate a code
HMACAlgorithm	getAlgorithm()
int	getPasswordLength()
byte[]	getSecret()
protected URI	getURI(String type, String path, Map<String,String> query)	Generate an OTPAuth URI
boolean	verify(String code, long counter)	Checks whether a code is valid for a specific counter with a delay window of 0
boolean	verify(String code, long counter, int delayWindow)	Checks whether a code is valid for a specific counter taking a delay window into account

Methods inherited from class java.lang.Object

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

Field Details

passwordLength

protected final int passwordLength

Number of digits for generated code in range 6...8, defaults to 6

algorithm

protected final HMACAlgorithm algorithm

Hashing algorithm used to generate code, defaults to SHA1

secret

protected final byte[] secret

Secret key used to generate the code, this should be a base32 string

Constructor Details

OTPGenerator

protected OTPGenerator(int passwordLength, HMACAlgorithm algorithm, byte[] secret)

Constructs the generator with custom password length and hashing algorithm

Parameters:

passwordLength - number of digits for generated code in range 6...8

algorithm - HMAC hash algorithm used to hash data

secret - used to generate hash

Method Details

getPasswordLength

public int getPasswordLength()

getAlgorithm

public HMACAlgorithm getAlgorithm()

getSecret

public byte[] getSecret()

verify

public boolean verify(String code, long counter)

Checks whether a code is valid for a specific counter with a delay window of 0

Parameters:

code - an OTP code

counter - how many times time interval has passed since 1970

Returns:

a boolean, true if code is valid, otherwise false

verify

public boolean verify(String code, long counter, int delayWindow)

Checks whether a code is valid for a specific counter taking a delay window into account

Parameters:

code - an OTP codee

counter - how many times time interval has passed since 1970

delayWindow - window in which a code can still be deemed valid

Returns:

a boolean, true if code is valid, otherwise false

generateCode

protected String generateCode(long counter) throws IllegalStateException

Generate a code

Parameters:

counter - how many times time interval has passed since 1970

Returns:

generated OTP code

Throws:

IllegalStateException - when hashing algorithm throws an error

getURI

protected URI getURI(String type, String path, Map<String,String> query) throws URISyntaxException

Generate an OTPAuth URI

Parameters:

type - of OTPAuth URI: totp or hotp

path - contains issuer and account name

query - items of URI

Returns:

created OTPAuth URI

Throws:

URISyntaxException - when URI cannot be created