RawRSASignature (6.0 API Documentation)

java.lang.Object
- java.security.SignatureSpi
- - iaik.security.rsa.RawRSASignature

```
public class RawRSASignature
extends java.security.SignatureSpi
```
This class represents a "raw" implementation of the RSA PKCS#1v1.5 digital signature algorithm (RSASSA-PKCS1-v1_5). Hashing and building a digest info object must be done by the application.
Digital signatures are used for ensuring data authentication and data integrity. RSA PKCS#1v1.5 based signature algorithms use a proper hash function for creating a message digest of the message to be signed. This class requires that the application does the hashing. Subsequently this message digest is encrypted with the RSA private key of the entity going to sign the message. Message and encrypted message digest together are sent to the intended receiver that verifies the signature by decrypting the received encrypted message digest with the corresponding RSA public key, and comparing it with the hash value derived from the received original message after hashing it with the same hash function as used by the entity that has sent the message.
This class follows the guidelines presented in PKCS#1) for implementing a signature algorithm based on the RSA encryption method.
An application wishing to sign some message or to verify some signature, generally has to perform four steps (in the following example, HASH has to be replaced by the name of the desired hash algorithm):
- First, the hash value over the data has to be prepared, e.g.:
```
 AlgorithmID hashAlgorithm = AlgorithmID.HASH; // e.g. AlgorithmID.sha1
 MessageDigest hashEngine = MessageDigest.getInstance(hashAlgorithm.getImplementationName());
 byte[] rawHash = hashEngine.digest(data);
 byte[] preparedHash = new DigestInfo(hashAlgorithm, rawHash).toByteArray();
 
```
- Second, an instance of the desired signature algorithm has to be created using a proper getInstance method, e.g.:
```
 Signature rawRsaSignatureEngine = Signature.getInstance("RSA", "IAIK");
 
```
- Third, the Signature object just created has to be properly initialized for signing a message respectively verifying a signature using a RSA private respectively RSA public key, e.g.:
  - Initialize for Signing: rawRsaSignatureEngine.initSign(rsaPrivateKey);
  - Initialize for Verifying: rawRsaSignatureEngine.initVerify(rsaPublicKey);
- Finally, if the Signature object has been initialized for signing, the prepared hash to be signed is supplied to it and subsequently the signature is created by calling the sign method returning the signature as byte array. Otherwise, if the Signature object has been initialized for verifying, first the prepared hash to be verified is supplied to the Signature object, and subsequently the signature is verified by calling the verify method, supplied with the byte array holding the corresponding signature value:
  - Supply the prepared hash to be signed, and subsequently sign it:
    rawRsaSignatureEngine.update(preparedHash); byte[] signature = rawRsaSignatureEngine.sign();
  - Supply the prepared hash to be verified, and verify the signature:
    rawRsaSignatureEngine.update(preparedHash); System.out.println("Signature " + (rawRsaSignatureEngine.verify(signature) ? "correct!" : "incorrect!"));
Version:

File Revision 11

See Also:
Signature

Field Summary

Fields
Modifier and Type Field and Description

protected java.io.ByteArrayOutputStream dataBuffer_
Data buffer to which the DigestInfo is written when supplied via an update method.
- Fields inherited from class java.security.SignatureSpi
  appRandom

Fields
Modifier and Type	Field and Description
`protected java.io.ByteArrayOutputStream`	`dataBuffer_` Data buffer to which the DigestInfo is written when supplied via an update method.

Constructor Summary

Constructors
Constructor and Description

RawRSASignature()
Creates a RSA Signature object.

Constructors
Constructor and Description
`RawRSASignature()` Creates a RSA Signature object.

Method Summary

Methods
Modifier and Type	Method and Description
`protected java.lang.Object`	`engineGetParameter(java.lang.String param)` This method is not implemented and only throws an InvalidParameterException
`protected void`	`engineInitSign(java.security.PrivateKey privateKey)` SPI: Initializes this Signature object with the given RSA private key for going to sign some data.
`protected void`	`engineInitSign(java.security.PrivateKey privateKey, java.security.SecureRandom random)` SPI: Initializes this Signature object with the given RSA private key and the given SecureRandom generator for going to sign some data.
`protected void`	`engineInitVerify(java.security.PublicKey pk)` SPI: Initializes this Signature object with the given RSA public key for performing a signature verification.
`protected void`	`engineSetParameter(java.lang.String param, java.lang.Object value)` This method is not implemented and only throws an InvalidParameterException
`protected byte[]`	`engineSign()` SPI: Returns a byte array holding the signature resulting from all already performed prepared hash update operations.
`protected void`	`engineUpdate(byte b)` SPI: Updates the data to be signed or verified with the specified byte.
`protected void`	`engineUpdate(byte[] b, int off, int len)` SPI: Updates the data to be signed or verified with the specified number of bytes, beginning at the specified offset within the given byte array.
`protected boolean`	`engineVerify(byte[] sigBytes)` Verifies the given signature of a message according to PKCS#1.

Methods inherited from class java.security.SignatureSpi
clone, engineGetParameters, engineSetParameter, engineSign, engineUpdate, engineVerify

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - dataBuffer_
```
protected java.io.ByteArrayOutputStream dataBuffer_
```
    Data buffer to which the DigestInfo is written when supplied via an update method.
- Constructor Detail
  - RawRSASignature
```
public RawRSASignature()
```
    Creates a RSA Signature object.
    Applications use
    Signature.getInstance("RSA");
    for creating a Signature object.
    See Also:
    Signature.getInstance(java.lang.String)
- Method Detail
  - engineInitVerify
```
protected void engineInitVerify(java.security.PublicKey pk)
                         throws java.security.InvalidKeyException
```
    SPI: Initializes this Signature object with the given RSA public key for performing a signature verification.
    
    Specified by:
    
    engineInitVerify in class java.security.SignatureSpi
    
    Parameters:
    pk - the RSA public key belonging to the RSA private key that has been used for signing.
    
    Throws:
    
    java.security.InvalidKeyException - if a key encoding error occurs
  - engineInitSign
```
protected void engineInitSign(java.security.PrivateKey privateKey)
                       throws java.security.InvalidKeyException
```
    SPI: Initializes this Signature object with the given RSA private key for going to sign some data.
    
    Specified by:
    
    engineInitSign in class java.security.SignatureSpi
    
    Parameters:
    privateKey - the RSA private key to be used for signing.
    
    Throws:
    
    java.security.InvalidKeyException - if a key encoding error occurs
  - engineInitSign
```
protected void engineInitSign(java.security.PrivateKey privateKey,
                  java.security.SecureRandom random)
                       throws java.security.InvalidKeyException
```
    SPI: Initializes this Signature object with the given RSA private key and the given SecureRandom generator for going to sign some data.
    
    Overrides:
    
    engineInitSign in class java.security.SignatureSpi
    
    Parameters:
    privateKey - the RSA private key to be used for signing.
    random - the random number generator
    
    Throws:
    
    java.security.InvalidKeyException - if a key decoding error occurs
  - engineSign
```
protected byte[] engineSign()
                     throws java.security.SignatureException
```
    SPI: Returns a byte array holding the signature resulting from all already performed prepared hash update operations.
    
    Specified by:
    
    engineSign in class java.security.SignatureSpi
    
    Returns:
    a byte array holding the signature value
    
    Throws:
    
    java.security.SignatureException - if an error occurs when creating the signature
  - engineVerify
```
protected boolean engineVerify(byte[] sigBytes)
                        throws java.security.SignatureException
```
    Verifies the given signature of a message according to PKCS#1.
    PKCS#1 defines a signature as bit string, which has to be converted into an octet string, RSA decrypted with the signer's RSA public key giving the prepared hash, which is normally an DER encoded DigestInfo object. This prepared hash is compared to the prepared hash provided by the application. If they are equal, the verification succeeded and true is returned, otherwise false is returned.
    Please notice that first step of bit-string-to-octet-string conversion already has to be done when calling this verify method. In this way the supplied sigBytes value has to be the octet string signature value.
    
    Specified by:
    
    engineVerify in class java.security.SignatureSpi
    
    Parameters:
    sigBytes - the signature bytes to be verified
    
    Returns:
    true if signature is OK, false otherwise
    
    Throws:
    
    java.security.SignatureException - if an error occurs when verifying the signature
  - engineUpdate
```
protected void engineUpdate(byte b)
```
    SPI: Updates the data to be signed or verified with the specified byte.
    
    Specified by:
    
    engineUpdate in class java.security.SignatureSpi
    
    Parameters:
    b - the byte to be used for updating.
  - engineUpdate
```
protected void engineUpdate(byte[] b,
                int off,
                int len)
```
    SPI: Updates the data to be signed or verified with the specified number of bytes, beginning at the specified offset within the given byte array.
    
    Specified by:
    
    engineUpdate in class java.security.SignatureSpi
    
    Parameters:
    b - the byte array holding the data to be used for this update operation.
    off - the offset, indicating the start position within the given byte array.
    len - the number of bytes to be obtained from the given byte array, starting at the given position.
  - engineSetParameter
```
protected void engineSetParameter(java.lang.String param,
                      java.lang.Object value)
                           throws java.security.InvalidParameterException
```
    This method is not implemented and only throws an InvalidParameterException
    
    Specified by:
    
    engineSetParameter in class java.security.SignatureSpi
    
    Throws:
    
    java.security.InvalidParameterException - This Method is not supported
  - engineGetParameter
```
protected java.lang.Object engineGetParameter(java.lang.String param)
                                       throws java.security.InvalidParameterException
```
    This method is not implemented and only throws an InvalidParameterException
    
    Specified by:
    
    engineGetParameter in class java.security.SignatureSpi
    
    Throws:
    
    java.security.InvalidParameterException - This Method is not supported

Class RawRSASignature

Field Summary

Fields inherited from class java.security.SignatureSpi

Constructor Summary

Method Summary

Methods inherited from class java.security.SignatureSpi

Methods inherited from class java.lang.Object

Field Detail

dataBuffer_

Constructor Detail

RawRSASignature

Method Detail

engineInitVerify

engineInitSign

engineInitSign

engineSign

engineVerify

engineUpdate

engineUpdate

engineSetParameter

engineGetParameter