org.cryptacular.generator.sp80038d

Class CounterNonce

java.lang.Object

org.cryptacular.generator.sp80038d.CounterNonce

All Implemented Interfaces:

Nonce

public class CounterNonce
extends Object
implements Nonce

Deterministic nonce generation strategy that uses a counter for the invocation field as described in NIST SP-800-38D, section 8.2.1. The invocation part of the sequence is always 64 bits (8 bytes) due to the use of a long, thus the length of the nonce is determined by the length of the fixed part: length = 8 + fixed.length.

NOTE: users of this class are responsible for maintaining the invocation count in order to support enforcement of constraints described in section 8.3; namely the following:

The total number of invocations of the authenticated encryption function shall not exceed 2³², including all IV lengths and all instances of the authenticated encryption function with the given key.

Instances of this class enforce this constraint by considering the nonce length, which determines whether the constraint applies, and the invocation count. The invocation count is incremented upon every invocation of generate() method. The current invocation count is accessible via getInvocations().

Instances of this class are thread safe.

Author:

Middleware Services

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_LENGTH Default nonce getLength is 12 bytes.
static long	MAX_INVOCATIONS Maximum invocations is 232.

Constructor Summary

Constructors

Constructor and Description
CounterNonce(byte[] fixed, long invocations) Creates a new instance.
CounterNonce(int fixed, long invocations) Creates a new instance.
CounterNonce(long fixed, long invocations) Creates a new instance.
CounterNonce(String fixed, long invocations) Creates a new instance.

Method Summary

Modifier and Type	Method and Description
byte[]	generate() Generates a nonce value.
long	getInvocations()
int	getLength()

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_LENGTH

public static final int DEFAULT_LENGTH

Default nonce getLength is 12 bytes.

See Also:

Constant Field Values

MAX_INVOCATIONS

public static final long MAX_INVOCATIONS

Maximum invocations is 2³². Does not apply to nonces with default getLength, 12.

See Also:

Constant Field Values

Constructor Detail

CounterNonce

public CounterNonce(String fixed,
                    long invocations)

Creates a new instance.

Parameters:

fixed - User-defined fixed field value.

invocations - Initial invocation count. The invocations field is incremented _before_ use in generate().

CounterNonce

public CounterNonce(int fixed,
                    long invocations)

Creates a new instance. Instances of this method produces nonces of the default length, 12, and are not subject to constraints on the number of invocations.

Parameters:

fixed - User-defined fixed field value.

invocations - Initial invocation count. The invocations field is incremented _before_ use in generate().

CounterNonce

public CounterNonce(long fixed,
                    long invocations)

Creates a new instance.

Parameters:

fixed - User-defined fixed field value.

invocations - Initial invocation count. The invocations field is incremented _before_ use in generate().

CounterNonce

public CounterNonce(byte[] fixed,
                    long invocations)

Creates a new instance.

Parameters:

fixed - User-defined fixed field value.

invocations - Initial invocation count. The invocations field is incremented _before_ use in generate().

Method Detail

generate

public byte[] generate()
                throws LimitException

Generates a nonce value.

Specified by:

generate in interface Nonce

Returns:

Nonce bytes.

Throws:

LimitException - When a limit imposed by the nonce generation strategy, if any, is exceeded.

getLength

public int getLength()

Specified by:

getLength in interface Nonce

Returns:

Length in bytes of generated nonce values.

getInvocations

public long getInvocations()

Returns:

Current invocation count.