Java Card API

signaturemessagerecovery

2017-05-22 17:33:39 M&W SmartCard 0

javacard.security

Interface SignatureMessageRecovery


A subclass of the abstract Signature class must implement this SignatureMessageRecovery interface to provide message recovery functionality. An instance implementing this interface is returned by theSignature.getInstance(byte, boolean)method when algorithm type with suffix *_MR is specified. e.g.Signature.ALG_RSA_SHA_ISO9796_MR . This interface provides specialized versions of some of the methods defined in the Signature class to provide message recovery functions. An alternate version of the sign() and verify() methods is supported here along with a new beginVerify method to allow the message encoded in the signature to be recovered. For signing a message with message recovery functionality, the user must cast the Signature object to this interface, initialize the object for signing with a private key using the init() method, and issue 0 or more update() method calls and then finally call the sign() method to obtain the signature. For recovering the encoded message and verifying functionality, the user must cast the Signature object to this interface, initialize the object for verifying with a public key using the init() method, first recover the message using the beginVerify() method and then issue 0 or more update() method calls and then finally call the verify() method to verify the signature. Note:A Signature object implementing this interface must throw CryptoException with CryptoException.ILLEGAL_USE reason code when one of the following methods applicable only to a Signature object which does not include message recovery functionality, is called:

  • init(Key, byte, byte[], short, short)


  • sign(byte[], short, short, byte[], short)


  • verify(byte[], short, short, byte[], short, short)


Since:

2.2.2

Method Summary
 short beginVerify (byte[] sigAndRecDataBuff,short buffOffset,short sigLength)          This method begins the verification sequence by recovering the message encoded within the signature itself and initializing the internal hash function.
 byte getAlgorithm ()          Gets the Signature algorithm.
 short getLength ()          Returns the byte length of the signature data.
 void init (Key  theKey,byte theMode)          Initializes the Signature object with the appropriate Key.
 short sign (byte[] inBuff,short inOffset,short inLength,byte[] sigBuff,short sigOffset,short[] recMsgLen,short recMsgLenOffset)          Generates the signature of all/last input data.
 void update (byte[] inBuff,short inOffset,short inLength)          Accumulates a signature of the input data.
 boolean verify (byte[] inBuff,short inOffset,short inLength)          Verifies the signature of all/last input data against the passed in signature.

 

Method Detail

init

void init(Key  theKey, byte theMode) throws CryptoException

Initializes the Signature object with the appropriate Key. This method should be used for algorithms which do not need initialization parameters or use default parameter values. init() must be used to update the Signature object with a new key. If the Key object is modified after invoking the init() method, the behavior of the update(), sign(), and verify() methods is unspecified.

Parameters:theKey - the key object to use for signing or verifying

theMode - one of MODE_SIGN or MODE_VERIFY

Throws: CryptoException- with the following reason codes:

  • CryptoException.ILLEGAL_VALUE if theMode option is an undefined value or if the Key is inconsistent with theMode or with the Signature implementation.


  • CryptoException.UNINITIALIZED_KEY if theKey instance is uninitialized.



beginVerify

short beginVerify(byte[] sigAndRecDataBuff, short buffOffset, short sigLength) throws CryptoException

This method begins the verification sequence by recovering the message encoded within the signature itself and initializing the internal hash function. The recovered message data overwrites the signature data in the sigAndRecDataBuff input byte array. Notes:

  • This method must be called during the verification sequenceprior to either the update() or the verify() methods during verification.


  • The trailing (sigLength - recovered message length) bytes ofsignature data in sigAndRecDataBuff may also be overwritten by this method.


Parameters:sigAndRecDataBuff - contains the signature data as input and also

contains the recoverable part of the message as output.

buffOffset - offset into the sigAndRecDataBuff array where data begins

for signature and where this method will start writing recovered message data.

sigLength - the length of signature data

Returns:byte length of recovered message data written to sigAndRecDataBuff

Throws: CryptoException- with the following reason codes:

  • CryptoException.ILLEGAL_USE for the following conditions:


  • if this object is initialized for signature sign mode


  • if sigLength is inconsistent with this Signature algorithm


  • if the decrypted message representative does not meet the algorithm specifications


  • if the bit length of the decrypted message representative is not a multiple of 8.



  • CryptoException.UNINITIALIZED_KEY if key not initialized.


  • CryptoException.INVALID_INIT if this Signature object is not initialized.



sign

short sign(byte[] inBuff, short inOffset, short inLength, byte[] sigBuff, short sigOffset, short[] recMsgLen, short recMsgLenOffset) throws CryptoException

Generates the signature of all/last input data. In addition, this method returns the number of bytes beginning with the first byte of the message that was encoded into the signature itself.The encoded message is called the recoverable message and its length is called the recoverable message length. This recoverable messageneed not be transmitted and can be recovered during verification. A call to this method also resets this Signature object to the state it was in when previously initialized via a call to init(). That is, the object is reset and available to sign another message. The input and output buffer data may overlap.

Parameters:inBuff - the input buffer of data to be signed

inOffset - the offset into the input buffer at which to begin signature generation

inLength - the byte length to sign

sigBuff - the output buffer to store signature data

sigOffset - the offset into sigBuff at which to begin signature data

recMsgLen - the output buffer containing the number of bytes of the recoverable message beginning with the first byte of the message that was encoded into the signature itself

recMsgLenOffset - offset into the recMsgLen output buffer where the byte length of the recoverable message is stored. Note that a single short value is stored at recMsgLenOffset offset.

Returns:number of bytes of signature output in sigBuff

Throws: CryptoException- with the following reason codes:

  • CryptoException.UNINITIALIZED_KEY if key not initialized.


  • CryptoException.INVALID_INIT if this Signature object is not initialized or initialized for signature verify mode.



verify

boolean verify(byte[] inBuff, short inOffset, short inLength) throws CryptoException

Verifies the signature of all/last input data against the passed in signature. A call to this method also resets this Signature object to the state it was in when previously initialized via a call to init(). That is, the object is reset and available to verify another message.

Parameters:inBuff - the input buffer of data to be verified

inOffset - the offset into the input buffer at which to begin signature generation

inLength - the byte length to sign

Returns:true if the signature verifies, false otherwise

Throws: CryptoException- with the following reason codes:

  • CryptoException.UNINITIALIZED_KEY if key not initialized.


  • CryptoException.INVALID_INIT if this Signature object is not initialized or initialized for signature sign mode.


  • CryptoException.ILLEGAL_USE if one of the following conditions is met:


  • if beginVerify method has not been called.




getAlgorithm

byte getAlgorithm()

Gets the Signature algorithm.

Returns:the algorithm code implemented by this Signature instance.


getLength

short getLength() throws CryptoException

Returns the byte length of the signature data.

Returns:the byte length of the signature data

Throws: CryptoException- with the following reason codes:

  • CryptoException.INVALID_INIT if this Signature object is not initialized.


  • CryptoException.UNINITIALIZED_KEY if key not initialized.



update

void update(byte[] inBuff, short inOffset, short inLength) throws CryptoException

Accumulates a signature of the input data. This method requires temporary storage ofintermediate results. In addition, if the input data length is not block aligned (multiple of block size) then additional internal storage may be allocated at this time to store a partial input data block. This may result in additional resource consumption and/or slow performance. This method should only be used if all the input data required for signing/verifying is not available in one byte array. If all of the input data required forsigning/verifying is located in a single byte array, use of the sign() or beginVerify method and verify() method is recommended. The sign() or verify() method must be called to complete processing of input data accumulated by one or more calls to the update() method. Note:

  • If inLength is 0 this method does nothing.


Parameters:inBuff - the input buffer of data to be signed/verified

inOffset - the offset into the input buffer where input data begins

inLength - the byte length to sign/verify

Throws: CryptoException- with the following reason codes:

  • CryptoException.UNINITIALIZED_KEY if key not initialized.


  • CryptoException.INVALID_INIT if this Signature object is not initialized.


  • CryptoException.ILLEGAL_USE if the mode set in the init() method is MODE_VERIFY and the beginVerify() method is not yet called.


See Also:sign(byte[], short, short, byte[], short, short[], short) ,verify(byte[], short, short)


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