iaik.security.rsa

Class RSAOaepKeyPairGenerator

java.lang.Object

java.security.KeyPairGeneratorSpi

java.security.KeyPairGenerator

iaik.security.rsa.RSAKeyPairGenerator

iaik.security.rsa.RSAOaepKeyPairGenerator

All Implemented Interfaces:

OaepKeyPairGenerator

public class RSAOaepKeyPairGenerator
extends RSAKeyPairGenerator
implements OaepKeyPairGenerator

KeyPairGenerator for generating RSAES-OAEP keys according to RFC 4055.

If no initialize() method of this key pair generator is called, it defaults to initialize(2048).
The algorithm used for key generation is according IEEE P1363.

RSAES-OAEP keys (RSAOaepPublicKey, RSAOaepPrivateKey) differ from ordinary PKCS#1 RSA keys (RSAPublicKey, RSAPrivateKey) only in that RSAES-OAEP keys may contain OAEP parameters. If RSAES-OAEP keys do not contain parameters they may be used for OAEP based en/decryption with any OAEP parameters. However, if RSAES-OAEP keys contain OAEP parameters they must be only used with the hash algorithm and mask generation function that are specified by their parameters (see RFC 4055):

 RSAES-OAEP-params  ::=  SEQUENCE  {
   hashFunc          [0] AlgorithmIdentifier DEFAULT
                            sha1Identifier,
   maskGenFunc       [1] AlgorithmIdentifier DEFAULT
                            mgf1SHA1Identifier,
   pSourceFunc       [2] AlgorithmIdentifier DEFAULT
                            pSpecifiedEmptyIdentifier  }
 
 
  pSpecifiedEmptyIdentifier  AlgorithmIdentifier  ::=
                      { id-pSpecified, nullOctetString }
 
  nullOctetString  OCTET STRING (SIZE (0))  ::=  { ''H }
 

An application wishing to create a RSAES-OAEP key pair to be used for OAEP based encryption with the RSA algorithm, uses a proper getInstance method of the java.security.KeyPairGenerator class, which subsequently maybe casted to RSAOaepKeyPairGenerator for performing an algorithm-specific initialization with proper RSAES-OAEP parameters. If an algorithm-specific initialization is not required, the cast to RSAOaepKeyPairGenerator can be omitted (in this case no parameters will be included in the RSA-OAEP generated keys and they maybe used with any OAEP parameters).

Generally four steps have to be performed for creating a RSAES-OAEP KeyPair by using a proper KeyPairGenerator:

• First the KeyPairGenerator has to be instantiated thereby specifying "RSAES-OAEP" as algorithm name:

   KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSAES-OAEP", "IAIK");
   

• Second, the KeyPairGenerator just created may be initialized using a proper initialize method. For initializing the generator to create keys with a modulus length of, e.g., 2048 bits, this can be explicitly specified (when not initializing the generator explicitly, per default the modulus length is set to 2048 bits):

   keyGen.initialize(2048);
   

• Third the key pair is created by calling generateKeyPair():

   KeyPair keyPair = keyGen.generateKeyPair();
   

• And finally the keys have to be got from the key pair just created:

   RSAOaepPrivateKey privateKey = (RSAOaepPrivateKey) keyPair.getPrivate();
   RSAOaepPublicKey publicKey = (RSAOaepPublicKey) keyPair.getPublic();
   

For performing an algorithm-specific initialization with particular RSA OAEP parameters an explicit cast of the KeyPairGenerator may be necessary for obtaining a specific RSAOaepKeyPairGenerator to be initialized with the desired RSA-OAEP parameters which have to be supplied as RSAOaepParameterSpec object, e.g.:

 RSAOaepKeyPairGenerator rsaOaepkeyGen = (RSAOaepKeyPairGenerator) keyGen;
 // create OAEP parameters for specifying hash, mgf and pSource algorithms:
 // hash, mgf and pSource algorithm ids
 AlgorithmID hashID = (AlgorithmID) AlgorithmID.sha512.clone();
 AlgorithmID mgfID = (AlgorithmID) AlgorithmID.mgf1.clone();
 mgfID.setParameter(hashID.toASN1Object());
 AlgorithmID pSourceID = (AlgorithmID) AlgorithmID.pSpecified.clone();
 pSourceID.setParameter(new OCTET_STRING());
 // hash and mgf engines
 MessageDigest hashEngine = hashID.getMessageDigestInstance();
 MaskGenerationAlgorithm mgfEngine = mgfID.getMaskGenerationAlgorithmInstance();
 MGF1ParameterSpec mgf1ParamSpec = new MGF1ParameterSpec(hashID);
 mgf1ParamSpec.setHashEngine(hashEngine);
 mgfEngine.setParameters(mgf1ParamSpec);
 // create the RSAOaepParameterSpec
 RSAOaepParameterSpec oaepParamSpec = new RSAOaepParameterSpec(hashID, mgfID,
     pSourceID);
 // set engines
 oaepParamSpec.setHashEngine(hashEngine);
 oaepParamSpec.setMGFEngine(mgfEngine);
 // initialize key pair generator
 rsaOaepkeyGen.initialize(2048, oaepParamSpec);
 KeyPair keyPair = rsaOaepkeyGen.generateKeyPair();
 RSAOaepPublicKey publicKey = (RSAOaepPublicKey) keyPair.getPublic();
 RSAOaepPrivateKey privateKey = (RSAOaepPrivateKey) keyPair.getPrivate();
 

RSAES-OAEP keys must be only used for en/decryption purposes with the RSAES-OAEP encryption scheme. For using a RSAOaepPublicKey with a Cipher engine, "OAEP" has to be specified as padding scheme when instantiating the Cipher object:

 Cipher rsaOaep = Cipher.getInstance("RSA/ECB/OAEP", "IAIK");
 

When now initializing the Cipher with an RSAES-OAEP key that contains OAEP parameters, the hash algorithm, mask generation function and pSource algorithm are taken from the public key parameters:

 rsaOaep.init(Cipher.ENCRYPT_MODE, publicKey); 
 // the data to be encrypted (e.g. secret key material):
 byte[] data = ...;
 // encrypt data  
 byte[] encrypted = rsaOaep.doFinal(data);
 

For decrypting the encrypted data you will have to use the right RSAES-OAEP RSAOaepPrivateKey:

 Cipher rsaOaep = Cipher.getInstance("RSA/ECB/OAEP", "IAIK");
 rsaOaep.init(Cipher.DECRYPT_MODE, privateKey); 
 // decrypt data  
 byte[] decrypted = rsaOaep.doFinal(encrypted);

Version:

File Revision 6

See Also:

RSAOaepPublicKey, RSAOaepPrivateKey, RSAOaepKeyFactory, RSAOaepParameterSpec, KeyPairGenerator, KeyPair

Field Summary

Fields inherited from class iaik.security.rsa.RSAKeyPairGenerator

initialized, keylen, public_exponent, random

Constructor Summary

Constructors

Constructor and Description
RSAOaepKeyPairGenerator() Default constructor for creating a RSAOaepKeyPairGenerator object.

Method Summary

Methods

Modifier and Type	Method and Description
void	initialize(java.security.spec.AlgorithmParameterSpec params) Initializes the key pair generator using the specified OAEP parameters.
void	initialize(java.security.spec.AlgorithmParameterSpec params, java.security.SecureRandom random) Initializes the key pair generator using the specified OAEP parameters and random number generator.
void	initialize(int strength, java.security.spec.AlgorithmParameterSpec params) Initializes this key pair generator using the specified "strength" (desired key length in bits) and OAEP parameters.
void	initialize(int strength, java.security.spec.AlgorithmParameterSpec params, java.security.SecureRandom secureRandom) Initializes this key pair generator using the specified "strength" (desired key length in bits), source of random bits, and OAEP parameters.
void	initialize(int strength, java.math.BigInteger publicExponent, java.security.spec.AlgorithmParameterSpec params, java.security.SecureRandom secureRandom) Initializes this key pair generator using the specified "strength" (desired key length in bits), public exponent, source of random bits, and OAEP parameters.

Methods inherited from class iaik.security.rsa.RSAKeyPairGenerator

generateKeyPair, initialize, initialize, initialize

Methods inherited from class java.security.KeyPairGenerator

genKeyPair, getAlgorithm, getInstance, getInstance, getInstance, getProvider

Methods inherited from class java.lang.Object

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

Constructor Detail

RSAOaepKeyPairGenerator

public RSAOaepKeyPairGenerator()

Default constructor for creating a RSAOaepKeyPairGenerator object. Required for dynamic object creation. An application typically will not use this constructor for creating a RSAOaepKeyPairGenerator. Rather it will use a proper KeyPairGenerator.getInstance method:

 KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSAES-OAEP", "IAIK");
 

See Also:

KeyPairGenerator

Method Detail

initialize

public void initialize(java.security.spec.AlgorithmParameterSpec params)
                throws java.security.InvalidAlgorithmParameterException

Initializes the key pair generator using the specified OAEP parameters.

Specified by:

initialize in interface OaepKeyPairGenerator

Overrides:

initialize in class RSAKeyPairGenerator

Parameters:

params - the OAEP parameters to be set for the RSAES-OAEP keys

Throws:

java.security.InvalidAlgorithmParameterException - if the supplied parameters do not represent OAEP parameters or java.security.spec.RSAKeyGenParameterSpec or the KeyPairGenerator cannot be initialized from the parameters

initialize

public void initialize(java.security.spec.AlgorithmParameterSpec params,
              java.security.SecureRandom random)
                throws java.security.InvalidAlgorithmParameterException

Initializes the key pair generator using the specified OAEP parameters and random number generator.

Specified by:

initialize in interface OaepKeyPairGenerator

Overrides:

initialize in class RSAKeyPairGenerator

Parameters:

params - the OAEP parameters to be set for the RSAES-OAEP keys

secureRandom - the random seed

Throws:

java.security.InvalidAlgorithmParameterException - if the supplied parameters do not represent OAEP parameters or java.security.spec.RSAKeyGenParameterSpec or the KeyPairGenerator cannot be initialized from the parameters

initialize

public void initialize(int strength,
              java.security.spec.AlgorithmParameterSpec params)
                throws java.security.InvalidParameterException

Initializes this key pair generator using the specified "strength" (desired key length in bits) and OAEP parameters. When using this initialization method, an explicit cast to RSAOaepKeyPairGenerator is required:

 RSAOaepKeyPairGenerator keyGen = (RSAOaepKeyPairGenerator)KeyPairGenerator.getInstance("RSAES-OAEP", "IAIK");
 keyGen.initialize(strength, oaepParamSpec, secureRandom);
 ...
 

Specified by:

initialize in interface OaepKeyPairGenerator

Parameters:

strength - keyLength the length of the key in bits.

params - the OAEP parameters to be set for the RSAES-OAEP keys

Throws:

java.security.InvalidParameterException - if the supplied parameters do not represent OAEP parameters or java.security.spec.RSAKeyGenParameterSpec or the KeyPairGenerator cannot be initialized from the parameters

initialize

public void initialize(int strength,
              java.security.spec.AlgorithmParameterSpec params,
              java.security.SecureRandom secureRandom)
                throws java.security.InvalidParameterException

Initializes this key pair generator using the specified "strength" (desired key length in bits), source of random bits, and OAEP parameters. When using this initialization method, an explicit cast to RSAOaepKeyPairGenerator is required:

 RSAOaepKeyPairGenerator keyGen = (RSAOaepKeyPairGenerator)KeyPairGenerator.getInstance("RSAES-OAEP", "IAIK");
 keyGen.initialize(strength, oaepParamSpec, secureRandom);
 ...
 

Specified by:

initialize in interface OaepKeyPairGenerator

Parameters:

strength - keyLength the length of the key in bits.

params - the OAEP parameters to be set for the RSAES-OAEP keys

secureRandom - the random seed

Throws:

java.security.InvalidParameterException - if the supplied parameters do not represent OAEP parameters or java.security.spec.RSAKeyGenParameterSpec or the KeyPairGenerator cannot be initialized from the parameters

initialize

public void initialize(int strength,
              java.math.BigInteger publicExponent,
              java.security.spec.AlgorithmParameterSpec params,
              java.security.SecureRandom secureRandom)
                throws java.security.InvalidParameterException

Initializes this key pair generator using the specified "strength" (desired key length in bits), public exponent, source of random bits, and OAEP parameters. When using this initialization method, an explicit cast to RSAOaepKeyPairGenerator is required:

 RSAOaepKeyPairGenerator keyGen = (RSAOaepKeyPairGenerator)KeyPairGenerator.getInstance("RSAES-OAEP", "IAIK");
 keyGen.initialize(strength, publicExponent, oaepParamSpec, secureRandom);
 ...
 

Specified by:

initialize in interface OaepKeyPairGenerator

Parameters:

strength - keyLength the length of the key in bits.

publicExponent - the public exponent

params - the OAEP parameters to be set for the RSAES-OAEP keys

secureRandom - the random seed

Throws:

java.security.InvalidParameterException - if the supplied parameters do not represent OAEP parameters or java.security.spec.RSAKeyGenParameterSpec or the KeyPairGenerator cannot be initialized from the parameters