Package com.eatthepath.otp

Class HmacOneTimePasswordGenerator

java.lang.Object

com.eatthepath.otp.HmacOneTimePasswordGenerator

public class HmacOneTimePasswordGenerator
extends Object

Generates HMAC-based one-time passwords (HOTP) as specified in RFC 4226. HmacOneTimePasswordGenerator instances are thread-safe and may be shared between threads.

Author:

Jon Chambers

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_PASSWORD_LENGTH	The default length, in decimal digits, for one-time passwords.

Constructor Summary

Constructors

Constructor	Description
HmacOneTimePasswordGenerator()	Creates a new HMAC-based one-time password (HOTP) generator using a default password length (6 digits).
HmacOneTimePasswordGenerator(int passwordLength)	Creates a new HMAC-based one-time password (HOTP) generator using the given password length.

Method Summary

Modifier and Type	Method	Description
int	generateOneTimePassword(Key key, long counter)	Generates a one-time password using the given key and counter value.
String	generateOneTimePasswordString(Key key, long counter)	Generates a one-time password using the given key and counter value and formats it as a string using the system default locale.
String	generateOneTimePasswordString(Key key, long counter, Locale locale)	Generates a one-time password using the given key and counter value and formats it as a string using the given locale.
String	getAlgorithm()	Returns the name of the HMAC algorithm used by this generator.
int	getPasswordLength()	Returns the length, in decimal digits, of passwords produced by this generator.

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_PASSWORD_LENGTH

public static final int DEFAULT_PASSWORD_LENGTH

The default length, in decimal digits, for one-time passwords.

See Also:

• Constant Field Values

Constructor Details

HmacOneTimePasswordGenerator

public HmacOneTimePasswordGenerator()

Creates a new HMAC-based one-time password (HOTP) generator using a default password length (6 digits).

HmacOneTimePasswordGenerator

public HmacOneTimePasswordGenerator(int passwordLength)

Creates a new HMAC-based one-time password (HOTP) generator using the given password length.

Parameters:

passwordLength - the length, in decimal digits, of the one-time passwords to be generated; must be between 6 and 8, inclusive

Method Details

generateOneTimePassword

public int generateOneTimePassword(Key key,
 long counter)
                            throws InvalidKeyException

Generates a one-time password using the given key and counter value.

Parameters:

key - the key to be used to generate the password

counter - the counter value for which to generate the password

Returns:

an integer representation of a one-time password; callers will need to format the password for display on their own

Throws:

InvalidKeyException - if the given key is inappropriate for initializing the Mac for this generator

generateOneTimePasswordString

public String generateOneTimePasswordString(Key key,
 long counter)
                                     throws InvalidKeyException

Generates a one-time password using the given key and counter value and formats it as a string using the system default locale.

Parameters:

key - the key to be used to generate the password

counter - the counter value for which to generate the password

Returns:

a string representation of a one-time password

Throws:

InvalidKeyException - if the given key is inappropriate for initializing the Mac for this generator

See Also:

• Locale.getDefault()

generateOneTimePasswordString

public String generateOneTimePasswordString(Key key,
 long counter,
 Locale locale)
                                     throws InvalidKeyException

Generates a one-time password using the given key and counter value and formats it as a string using the given locale.

Parameters:

key - the key to be used to generate the password

counter - the counter value for which to generate the password

locale - the locale to apply during formatting

Returns:

a string representation of a one-time password

Throws:

InvalidKeyException - if the given key is inappropriate for initializing the Mac for this generator

getPasswordLength

public int getPasswordLength()

Returns the length, in decimal digits, of passwords produced by this generator.

Returns:

the length, in decimal digits, of passwords produced by this generator

getAlgorithm

public String getAlgorithm()

Returns the name of the HMAC algorithm used by this generator.

Returns:

the name of the HMAC algorithm used by this generator