de.flexiprovider.pqc.ecc.mceliece
Class McElieceFujisakiCipher

java.lang.Object
  |
  +--javax.crypto.CipherSpi
        |
        +--de.flexiprovider.api.Cipher
              |
              +--de.flexiprovider.api.AsymmetricHybridCipher
                    |
                    +--de.flexiprovider.pqc.ecc.mceliece.McElieceFujisakiCipher

public class McElieceFujisakiCipher

extends AsymmetricHybridCipher

This class implements the Fujisaki/Okamoto conversion of the McEliecePKCS. Fujisaki and Okamoto propose hybrid encryption that merges a symmetric encryption scheme which is secure in the find-guess model with an asymmetric one-way encryption scheme which is sufficiently probabilistic to obtain a public key cryptosystem which is CCA2-secure. For details, see D. Engelbert, R. Overbeck, A. Schmidt, "A summary of the development of the McEliece Cryptosystem", technical report.

This class extends the CipherSpi class.

The Fujisaki/Okamoto conversion can be used as follows:

To encrypt a message, the following steps have to be performed:

 // setup
 KeyPairGenerator kpg = KeyPairGenerator.getInstance("McEliece", "FlexiPQC");
 KeyPair keys = kpg.generateKeyPair();
 McElieceCCA2PublicKey pubK = (McElieceCCA2PublicKey) keys.getPublic();
 McElieceCCA2PrivateKey privK = (McElieceCCA2PrivateKey) keys.getPrivate();
 SecureRandom sr = Registry.getSecureRandom();
 Cipher cipher = Cipher.getInstance("McElieceFujisakiConversion");
 
 // the string to encrypt and decrypt
 String m = "This is a test for the Fujisaki conversion of the McEliecePKCS.";
 byte[] mBytes = m.getBytes();
 
 // initialize cipher in encrypt mode
 cipher.init(Cipher.ENCRYPT_MODE, pubK, sr);
 
 // encrypt
 byte[] cBytes = cipher.doFinal(mBytes);
 

To decrypt, the following steps have to be performed (using setup from above):

 // initialize cipher in decrypt mode
 cipher.init(Cipher.DECRYPT_MODE, privK);
 
 // decrypt
 byte[] decBytes = cipher.doFinal(cBytes);
 String newM = new String(decBytes);
 

Field Summary

static java.lang.String

OID The OID of the algorithm.

Fields inherited from class de.flexiprovider.api.AsymmetricHybridCipher

paramSpec

Fields inherited from class de.flexiprovider.api.Cipher

DECRYPT_MODE, ENCRYPT_MODE, opMode

Constructor Summary

McElieceFujisakiCipher()

Method Summary

protected int	decryptOutputSize(int inLen) Compute the output size of an update() or doFinal() operation of a hybrid asymmetric cipher in decryption mode when given input of the specified length.
byte[]	doFinal(byte[] input, int inOff, int inLen) Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
protected int	encryptOutputSize(int inLen) Compute the output size of an update() or doFinal() operation of a hybrid asymmetric cipher in encryption mode when given input of the specified length.
int	getKeySize(Key key) Return the key size of the given key object.
java.lang.String	getName()
protected void	initCipherDecrypt(Key key, AlgorithmParameterSpec params) Initialize the AsymmetricHybridCipher with a certain key for data encryption.
protected void	initCipherEncrypt(Key key, AlgorithmParameterSpec params, SecureRandom secureRand) Initialize the AsymmetricHybridCipher with a certain key for data encryption.
protected byte[]	messageDecrypt(byte[] input)
protected byte[]	messageEncrypt(byte[] input)
byte[]	update(byte[] input, int inOff, int inLen) Continue a multiple-part encryption or decryption operation.

Methods inherited from class de.flexiprovider.api.AsymmetricHybridCipher

doFinal, getBlockSize, getIV, getOutputSize, getParameters, initDecrypt, initDecrypt, initEncrypt, initEncrypt, initEncrypt, initEncrypt, setMode, setPadding, update

Methods inherited from class de.flexiprovider.api.Cipher

doFinal, doFinal, engineDoFinal, engineDoFinal, engineGetBlockSize, engineGetIV, engineGetKeySize, engineGetOutputSize, engineGetParameters, engineInit, engineInit, engineInit, engineSetMode, engineSetPadding, engineUpdate, engineUpdate, update

Methods inherited from class java.lang.Object

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

Field Detail

OID

public static final java.lang.String OID

The OID of the algorithm.

Constructor Detail

McElieceFujisakiCipher

public McElieceFujisakiCipher()

Method Detail

getName

public java.lang.String getName()

Overrides:

getName in class Cipher

Returns:

the name of this cipher

getKeySize

public int getKeySize(Key key)
               throws InvalidKeyException

Return the key size of the given key object. Checks whether the key object is an instance of McElieceCCA2PublicKey or McElieceCCA2PrivateKey.

Overrides:

getKeySize in class Cipher

Parameters:

key - the key object

Returns:

the keysize of the given key object

Throws:

InvalidKeyException - if the key is invalid

encryptOutputSize

protected int encryptOutputSize(int inLen)

Description copied from class: AsymmetricHybridCipher

Compute the output size of an update() or doFinal() operation of a hybrid asymmetric cipher in encryption mode when given input of the specified length.

Overrides:

encryptOutputSize in class AsymmetricHybridCipher

Following copied from class: de.flexiprovider.api.AsymmetricHybridCipher

Parameters:

inLen - the length of the input

Returns:

the output size

decryptOutputSize

protected int decryptOutputSize(int inLen)

Description copied from class: AsymmetricHybridCipher

Compute the output size of an update() or doFinal() operation of a hybrid asymmetric cipher in decryption mode when given input of the specified length.

Overrides:

decryptOutputSize in class AsymmetricHybridCipher

Following copied from class: de.flexiprovider.api.AsymmetricHybridCipher

Parameters:

inLen - the length of the input

Returns:

the output size

update

public byte[] update(byte[] input,
                     int inOff,
                     int inLen)

Continue a multiple-part encryption or decryption operation.

Overrides:

update in class AsymmetricHybridCipher

Parameters:

input - byte array containing the next part of the input

inOff - index in the array where the input starts

inLen - length of the input

Returns:

the processed byte array.

doFinal

public byte[] doFinal(byte[] input,
                      int inOff,
                      int inLen)
               throws BadPaddingException

Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. The data is encrypted or decrypted, depending on how this cipher was initialized.

Overrides:

doFinal in class AsymmetricHybridCipher

Parameters:

input - the input buffer

inOff - the offset in input where the input starts

inLen - the input length

Returns:

the new buffer with the result

Throws:

BadPaddingException - on decryption errors.

initCipherEncrypt

protected void initCipherEncrypt(Key key,
                                 AlgorithmParameterSpec params,
                                 SecureRandom secureRand)
                          throws InvalidKeyException,
                                 InvalidAlgorithmParameterException

Description copied from class: AsymmetricHybridCipher

Initialize the AsymmetricHybridCipher with a certain key for data encryption.

Overrides:

initCipherEncrypt in class AsymmetricHybridCipher

Following copied from class: de.flexiprovider.api.AsymmetricHybridCipher

Parameters:

key - the key which has to be used to encrypt data

params - the algorithm parameters

sr - the source of randomness

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher.

InvalidAlgorithmParameterException - if the given parameters are inappropriate for initializing this cipher.

initCipherDecrypt

protected void initCipherDecrypt(Key key,
                                 AlgorithmParameterSpec params)
                          throws InvalidKeyException,
                                 InvalidAlgorithmParameterException

Description copied from class: AsymmetricHybridCipher

Initialize the AsymmetricHybridCipher with a certain key for data encryption.

Overrides:

initCipherDecrypt in class AsymmetricHybridCipher

Following copied from class: de.flexiprovider.api.AsymmetricHybridCipher

Parameters:

key - the key which has to be used to decrypt data

params - the algorithm parameters

Throws:

InvalidKeyException - if the given key is inappropriate for initializing this cipher

InvalidAlgorithmParameterException - if the given parameters are inappropriate for initializing this cipher.

messageEncrypt

protected byte[] messageEncrypt(byte[] input)

messageDecrypt

protected byte[] messageDecrypt(byte[] input)
                         throws BadPaddingException