de.flexiprovider.core.rsa
Class UnlimitedLengthRSA

java.lang.Object
  |
  +--javax.crypto.CipherSpi
        |
        +--de.flexiprovider.api.Cipher
              |
              +--de.flexiprovider.api.AsymmetricBlockCipher
                    |
                    +--de.flexiprovider.core.rsa.RSA_PKCS1_v1_5
                          |
                          +--de.flexiprovider.core.rsa.UnlimitedLengthRSA

public class UnlimitedLengthRSA

extends RSA_PKCS1_v1_5

Implements the PKCS1v5 RSA as a cipher with unlimited length for plaintexts and ciphertexts. First it truncates a big message to smaller messages that can be processed by a standard RSA encryption. This depends also on the key size. For example for a 1024 bits key only up to 117 (128-11) bytes can be en/decrypted. Upon an input of 304 bytes, first three submessages are created. The first one is 70 (304-2*117) bytes long and the other two 117. Each message is encrypted with a normal PKCS1v5 RSA encryption. The ciphertext is 384 (3*128) bytes long. This is also truncated to three messages of 128 bytes which are also decrypted by a normal RSA operation.

Author:

Michael Gaber

Field Summary

static java.lang.String

NAME

Fields inherited from class de.flexiprovider.core.rsa.RSA_PKCS1_v1_5

OID

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

UnlimitedLengthRSA()

Method Summary

protected void	checkLength(int inLength) Checks whether the plaintext or the ciphertext have correct sizes.
java.lang.String	getName() Return the name of the encrpytion algorithm.
protected byte[]	messageDecrypt(byte[] input) Decrypts this message of unlimited length.
protected byte[]	messageEncrypt(byte[] input) Encrypts this message of unlimited length.

Methods inherited from class de.flexiprovider.core.rsa.RSA_PKCS1_v1_5

getKeySize, initCipherDecrypt, initCipherEncrypt

Methods inherited from class de.flexiprovider.api.AsymmetricBlockCipher

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

NAME

public static final java.lang.String NAME

Constructor Detail

UnlimitedLengthRSA

public UnlimitedLengthRSA()

Method Detail

messageDecrypt

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

Decrypts this message of unlimited length. The length of the message however still needs to be a multiple of a normal RSA to-be-decrypted message.

Overrides:

messageDecrypt in class RSA_PKCS1_v1_5

Returns:

the decrypted message.

messageEncrypt

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

Encrypts this message of unlimited length.

Overrides:

messageEncrypt in class RSA_PKCS1_v1_5

Returns:

the ciphertext message.

getName

public java.lang.String getName()

Return the name of the encrpytion algorithm.

Overrides:

getName in class RSA_PKCS1_v1_5

Returns:

the name of the encryption algorithm.

checkLength

protected void checkLength(int inLength)
                    throws IllegalBlockSizeException

Checks whether the plaintext or the ciphertext have correct sizes. While for plaintexts there are no restrictions, the ciphertext must be a multiple of a normal RSA to-be-decrypted message.

Overrides:

checkLength in class AsymmetricBlockCipher

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

Parameters:

inLen - length of the input to check

Throws:

IllegalBlockSizeException - if the input length is invalid.