Package com.bastiaanjansen.otp

Class HOTP

java.lang.Object

com.bastiaanjansen.otp.HOTP

All Implemented Interfaces:

HOTPGenerator, HOTPVerifier

public final class HOTP
extends Object
implements HOTPGenerator, HOTPVerifier

Generates counter-based one-time passwords

Author:

Bastiaan Jansen

See Also:

OTP

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	HOTP.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

Method Summary

Modifier and Type	Method	Description
static HOTP	fromURI(URI uri)	Build a TOTPGenerator from an OTPAuth URI
String	generate(long counter)	Generate a counter-based one-time password
HMACAlgorithm	getAlgorithm()
int	getPasswordLength()
byte[]	getSecret()
URI	getURI(int counter, String issuer)	Create an OTPAuth URI for easy user on-boarding with only an issuer
URI	getURI(int counter, String issuer, String account)	Create an OTPAuth URI for easy user on-boarding with an issuer and account name
protected URI	getURI(String type, String issuer, String account, 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
static HOTP	withDefaultValues(byte[] secret)	Create a com.bastiaanjansen.otp.HOTPGenerator with default values

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.bastiaanjansen.otp.HOTPVerifier

verify, verify

Field Detail

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

Method Detail

fromURI

public static HOTP fromURI(URI uri)
                    throws URISyntaxException

Build a TOTPGenerator from an OTPAuth URI

Parameters:

uri - OTPAuth URI

Returns:

HOTP

Throws:

URISyntaxException - when URI cannot be parsed

withDefaultValues

public static HOTP withDefaultValues(byte[] secret)

Create a com.bastiaanjansen.otp.HOTPGenerator with default values

Parameters:

secret - used to generate hash

Returns:

a com.bastiaanjansen.otp.HOTPGenerator with default values

generate

public String generate(long counter)
                throws IllegalArgumentException

Generate a counter-based one-time password

Specified by:

generate in interface HOTPGenerator

Parameters:

counter - how many times time interval has passed since 1970

Returns:

generated HOTP code

Throws:

IllegalArgumentException - when code could not be generated

getURI

public URI getURI(int counter,
                  String issuer)
           throws URISyntaxException

Create an OTPAuth URI for easy user on-boarding with only an issuer

Parameters:

counter - of URI

issuer - name for URI

Returns:

OTPAuth URI

Throws:

URISyntaxException - when URI cannot be created

getURI

public URI getURI(int counter,
                  String issuer,
                  String account)
           throws URISyntaxException

Create an OTPAuth URI for easy user on-boarding with an issuer and account name

Parameters:

counter - of URI

issuer - name for URI

account - name for URI

Returns:

OTPAuth URI

Throws:

URISyntaxException - when URI cannot be created

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

getURI

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

Generate an OTPAuth URI

Parameters:

type - of OTPAuth URI: totp or hotp

issuer - name for URI

account - name for URI

query - items of URI

Returns:

created OTPAuth URI

Throws:

URISyntaxException - when URI cannot be created