com.predic8.membrane.core.interceptor.authentication.session.totp

Class TotpCounter

java.lang.Object

com.predic8.membrane.core.interceptor.authentication.session.totp.TotpCounter

public class TotpCounter
extends Object

Counter whose value is a deterministic function of time as described in RFC 6238 "TOTP: Time-Based One-Time Password Algorithm".

The 64-bit counter assumes the value 0 at a predefined point in time and periodically increments its value by one periodically.

The value V of the counter at time instant T is:

 V = (T - T0) / TimeStep
 

where T0 is the earliest time instant at which the counter assumes the value 0, and TimeStep is the duration of time for which the values of the counter remain constant.

Note: All time instants are in seconds since UNIX epoch, and all time durations are in seconds.

Note: All time instants must be non-negative.

Thread-safety: Instances of this class are immutable and are thus thread-safe. Source: http://code.google.com/p/google-authenticator License: ASL 2.0

Author:

klyubin@google.com (Alex Klyubin)

Constructor Summary

Constructors

Constructor and Description
TotpCounter(long timeStep) Constructs a new TotpCounter that starts with the value 0 at time instant 0 (seconds since UNIX epoch) and increments its value with the specified frequency.
TotpCounter(long timeStep, long startTime) Constructs a new TotpCounter that starts with the value 0 at the specified time and increments its value with the specified frequency.

Method Summary

Modifier and Type	Method and Description
long	getStartTime() Gets the earliest time instant at which this counter assumes the value 0.
long	getTimeStep() Gets the frequency with which the value of this counter changes.
long	getValueAtTime(long time) Gets the value of this counter at the specified time.
long	getValueStartTime(long value) Gets the time when the counter assumes the specified value.

Methods inherited from class java.lang.Object

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

Constructor Detail

TotpCounter

public TotpCounter(long timeStep)

Constructs a new TotpCounter that starts with the value 0 at time instant 0 (seconds since UNIX epoch) and increments its value with the specified frequency.

Parameters:

timeStep - interval of time (seconds) between successive changes of this counter's value.

TotpCounter

public TotpCounter(long timeStep,
                   long startTime)

Constructs a new TotpCounter that starts with the value 0 at the specified time and increments its value with the specified frequency.

Parameters:

timeStep - interval of time (seconds) between successive changes of this counter's value.

startTime - the earliest time instant (seconds since UNIX epoch) at which this counter assumes the value 0.

Method Detail

getTimeStep

public long getTimeStep()

Gets the frequency with which the value of this counter changes.

Returns:

interval of time (seconds) between successive changes of this counter's value.

getStartTime

public long getStartTime()

Gets the earliest time instant at which this counter assumes the value 0.

Returns:

time (seconds since UNIX epoch).

getValueAtTime

public long getValueAtTime(long time)

Gets the value of this counter at the specified time.

Parameters:

time - time instant (seconds since UNIX epoch) for which to obtain the value.

Returns:

value of the counter at the time.

getValueStartTime

public long getValueStartTime(long value)

Gets the time when the counter assumes the specified value.

Parameters:

value - value.

Returns:

earliest time instant (seconds since UNIX epoch) when the counter assumes the value.