de.flexiprovider.pqc.ecc.mceliece
Class McEliecePKCS

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

public class McEliecePKCS

extends AsymmetricBlockCipher

This class implements the McEliece Public Key cryptosystem (McEliecePKCS). It was first described in R.J. McEliece, "A public key cryptosystem based on algebraic coding theory", DSN progress report, 42-44:114-116, 1978. The McEliecePKCS is the first cryptosystem which is based on error correcting codes. The trapdoor for the McEliece cryptosystem using Goppa codes is the knowledge of the Goppa polynomial used to generate the code.

The class extends the AsymmetricBlockCipher class.

The McEliecePKC can be used as follows:

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

 // The message which should be encrypted
 String message = "secret message";
 byte[] messageBytes = message.getBytes();
 
 // Generate KeySpec from encoded McEliece public key:
 KeySpec publicKeySpec = new X509EncodedKeySpec(encPublicKey);
 
 // Initialize the McEliece key factory:<br/>
 KeyFactory keyFactory = KeyFactory.getInstance("McEliece", "FlexiPQC");
 
 // Decode McEliece public key:<br/>
 PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
 
 // The source of randomness
 SecureRandom secureRand = Registry.getSecureRandom();
 
 // Obtain a McEliecePKC Cipher Object
 Cipher cipher = Cipher.getInstance("McEliecePKCS");
 
 // Initialize the cipher
 cipher.init(Cipher.ENCRYPT_MODE, publicKey, secureRand);
 
 // Finally encrypt the message
 byte[] ciphertextBytes = cipher.doFinal(messageBytes);
 

To decrypt a ciphertext, the following steps have to be performed:

 // Generate KeySpec from encoded McEliece private key:
 KeySpec publicKeySpec = new PKCS8EncodedKeySpec(encPrivateKey);
 
 // Initialize the McEliece key factory:<br/>
 KeyFactory keyFactory = KeyFactory.getInstance("McEliece", "FlexiPQC");
 
 // Decode McEliece private key:<br/>
 PublicKey privateKey = keyFactory.generatePrivate(privateKeySpec);
 
 // Obtain a McEliecePKC Cipher Object
 Cipher cipher = Cipher.getInstance("McEliecePKCS");
 
 // Initialize the cipher
 cipher.init(Cipher.DECRYPT_MODE, privateKey);
 
 // Finally decrypt the message
 byte[] messageBytes = cipher.doFinal(ciphertextBytes);
 String message = new String(messageBytes);
 

Author:

Elena Klintsevich

See Also:

AsymmetricBlockCipher

Field Summary

static java.lang.String

OID The OID of the algorithm.

Fields inherited from class de.flexiprovider.api.AsymmetricBlockCipher

buf, cipherTextSize, maxPlainTextSize, paramSpec

Fields inherited from class de.flexiprovider.api.Cipher

DECRYPT_MODE, ENCRYPT_MODE, opMode

Constructor Summary

McEliecePKCS()

Method Summary

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 block cipher with a private key for data decryption.
protected void	initCipherEncrypt(Key key, AlgorithmParameterSpec params, SecureRandom secureRandom) Initialize the block cipher with a public key for data encryption.
protected byte[]	messageDecrypt(byte[] input) Decrypt a ciphertext.
protected byte[]	messageEncrypt(byte[] input) Encrypt a plaintext.

Methods inherited from class de.flexiprovider.api.AsymmetricBlockCipher

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

McEliecePKCS

public McEliecePKCS()

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 McEliecePublicKey or McEliecePrivateKey.

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

initCipherEncrypt

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

Initialize the block cipher with a public key for data encryption. Currently, parameters are not supported.

Overrides:

initCipherEncrypt in class AsymmetricBlockCipher

Parameters:

key - the key which shall be used to encrypt data

params - the algorithm parameters

secureRandom - the source of randomness

Throws:

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

initCipherDecrypt

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

Initialize the block cipher with a private key for data decryption. Currently, parameters are not supported.

Overrides:

initCipherDecrypt in class AsymmetricBlockCipher

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.

messageEncrypt

protected byte[] messageEncrypt(byte[] input)

Encrypt a plaintext.

Overrides:

messageEncrypt in class AsymmetricBlockCipher

Parameters:

input - the plaintext

Returns:

the ciphertext

messageDecrypt

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

Decrypt a ciphertext.

Overrides:

messageDecrypt in class AsymmetricBlockCipher

Parameters:

input - the ciphertext

Returns:

the plaintext

Throws:

BadPaddingException - if the ciphertext is invalid.