Class InitializedMessageDigest

java.lang.Object

javacard.security.MessageDigest

javacard.security.InitializedMessageDigest

Direct Known Subclasses:

InitializedMessageDigest.OneShot

public abstract class InitializedMessageDigest
extends MessageDigest

The InitializedMessageDigest class is a subclass of the base class MessageDigest. This class is used to generate a hash representing a specified message but with the additional capability to set the state of the hash engine. This state is the intermediate state of the hash engine when a block-aligned portion of the message has been previously processed. Implementations of InitializedMessageDigest algorithms must extend this class and implement all the abstract methods.

A tear or card reset event resets a InitializedMessageDigest object to the initial state (state upon construction).

Even if a transaction is in progress, update of intermediate result state in the implementation instance shall not participate in the transaction.

Since:

2.2.2

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	InitializedMessageDigest.OneShot	The OneShot class is a specialization of the InitializedMessageDigest class intended to support efficient one-shot hash operations that may avoid persistent memory writes entirely.

Field Summary

Fields inherited from class MessageDigest

ALG_MD5, ALG_NULL, ALG_RIPEMD160, ALG_SHA, ALG_SHA_224, ALG_SHA_256, ALG_SHA_384, ALG_SHA_512, ALG_SHA3_224, ALG_SHA3_256, ALG_SHA3_384, ALG_SHA3_512, ALG_SM3, LENGTH_MD5, LENGTH_RIPEMD160, LENGTH_SHA, LENGTH_SHA_224, LENGTH_SHA_256, LENGTH_SHA_384, LENGTH_SHA_512, LENGTH_SHA3_224, LENGTH_SHA3_256, LENGTH_SHA3_384, LENGTH_SHA3_512, LENGTH_SM3

Modifier and Type	Field	Description
static final byte	ALG_MD5	Message Digest algorithm MD5.
static final byte	ALG_NULL	This constant indicates that there is no discrete message digest algorithm.
static final byte	ALG_RIPEMD160	Message Digest algorithm RIPE MD-160.
static final byte	ALG_SHA	Message Digest algorithm SHA-1.
static final byte	ALG_SHA_224	Message Digest algorithm SHA-224.
static final byte	ALG_SHA_256	Message Digest algorithm SHA-256.
static final byte	ALG_SHA_384	Message Digest algorithm SHA-384.
static final byte	ALG_SHA_512	Message Digest algorithm SHA-512.
static final byte	ALG_SHA3_224	Message Digest algorithm SHA3-224.
static final byte	ALG_SHA3_256	Message Digest algorithm SHA3-256.
static final byte	ALG_SHA3_384	Message Digest algorithm SHA3-384.
static final byte	ALG_SHA3_512	Message Digest algorithm SHA3-512.
static final byte	ALG_SM3	Message Digest algorithm SM3.
static final byte	LENGTH_MD5	Length of digest in bytes for MD5
static final byte	LENGTH_RIPEMD160	Length of digest in bytes for RIPE MD-160
static final byte	LENGTH_SHA	Length of digest in bytes for SHA-1
static final byte	LENGTH_SHA_224	Length of digest in bytes for SHA-224
static final byte	LENGTH_SHA_256	Length of digest in bytes for SHA-256
static final byte	LENGTH_SHA_384	Length of digest in bytes for SHA-384
static final byte	LENGTH_SHA_512	Length of digest in bytes for SHA-512
static final byte	LENGTH_SHA3_224	Length of digest in bytes for SHA3-224
static final byte	LENGTH_SHA3_256	Length of digest in bytes for SHA3-256
static final byte	LENGTH_SHA3_384	Length of digest in bytes for SHA3-384
static final byte	LENGTH_SHA3_512	Length of digest in bytes for SHA3-512
static final byte	LENGTH_SM3	Length of digest in bytes for SM3

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	InitializedMessageDigest()	protected constructor

Method Summary

Modifier and Type	Method	Description
abstract void	setInitialDigest(byte[] state, short stateOffset, short stateLength, byte[] digestedMsgLenBuf, short digestedMsgLenOffset, short digestedMsgLenLength)	This method sets the state of the hash engine in place of the default value used by the MessageDigest superclass.

Methods inherited from class MessageDigest

doFinal, doIntermediateMessageDigest, getAlgorithm, getInitializedMessageDigestInstance, getInstance, getLength, isIntermediateMessageDigestSupported, reset, update

Modifier and Type	Method	Description
abstract short	doFinal(byte[] inBuff, short inOffset, short inLength, byte[] outBuff, short outOffset)	Generates a hash of all/last input data.
abstract short	doIntermediateMessageDigest(byte[] outBuff, short outOffset)	Generates a hash of all/last input data.
abstract byte	getAlgorithm()	Gets the Message digest algorithm.
static final InitializedMessageDigest	getInitializedMessageDigestInstance(byte algorithm, boolean externalAccess)	Creates a InitializedMessageDigest object instance of the selected algorithm.
static final MessageDigest	getInstance(byte algorithm, boolean externalAccess)	Creates a MessageDigest object instance of the selected algorithm.
abstract byte	getLength()	Returns the byte length of the hash.
static final boolean	isIntermediateMessageDigestSupported(byte algorithm)	This method is used to determine if instances of MessageDigest or InitializedMessageDigest classes support intermediate hash calculation for a given algorithm.
abstract void	reset()	Resets the MessageDigest object to the initial state for further use.
abstract void	update(byte[] inBuff, short inOffset, short inLength)	Accumulates a hash of the input data.

Methods inherited from class Object

equals

Modifier and Type	Method	Description
boolean	equals(Object obj)	Compares two Objects for equality.

Constructor Details

InitializedMessageDigest

protected InitializedMessageDigest()

protected constructor

Method Details

setInitialDigest

public abstract void setInitialDigest(byte[] state,
 short stateOffset,
 short stateLength,
 byte[] digestedMsgLenBuf,
 short digestedMsgLenOffset,
 short digestedMsgLenLength)
                               throws CryptoException

This method sets the state of the hash engine in place of the default value used by the MessageDigest superclass. This state is the intermediate state of the hash engine when a block-aligned portion of the message has been previously processed. The remaining bytes of the message must be presented to this InitializedMessageDigest object via the update and doFinal methods to generate the final message digest.

Note:

• The maximum allowed value of the byte length of the first part of the message is algorithm specific

Parameters:

state - input buffer containing the intermediate state of the hash engine when a block-aligned portion of the message has been previously processed (using the same algorithm).

stateOffset - offset into state array where the state data begins

stateLength - the length of data in state array.

digestedMsgLenBuf - the byte array containing the number of bytes in the first part of the message that has previously been processed to obtain the specified intermediate state. The value must be a multiple of the block size defined by the hash algorithm.

digestedMsgLenOffset - the offset within digestedMsgLenBuf where the digested length begins (the bytes starting at this offset for digestedMsgLenLength bytes are concatenated to form the actual length of the message portion already processed)

digestedMsgLenLength - byte length of the value stored in digestedMsgLenBuf

Throws:

CryptoException - with the following reason codes:

• CryptoException.ILLEGAL_VALUE if the parameter stateLength is not equal to the intermediate hash value size of the algorithm or if the number of bytes in the first part of the message that has previously been hashed is 0 or not a multiple of the algorithm's block size or greater than the maximum length supported by the algorithm (see ALG_* algorithm descriptions ALG_SHA).