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gnu.java.security.sig.rsa
Class EME_PKCS1_V1_5  view EME_PKCS1_V1_5 download EME_PKCS1_V1_5.java

java.lang.Object
  extended bygnu.java.security.sig.rsa.EME_PKCS1_V1_5

public class EME_PKCS1_V1_5
extends java.lang.Object

An implementation of the EME-PKCS1-V1.5 encoding and decoding methods.

EME-PKCS1-V1.5 is parameterised by the entity k which is the byte count of an RSA public shared modulus.

References:

  1. Public-Key Cryptography Standards (PKCS) #1:
    RSA Cryptography Specifications Version 2.1.
    Jakob Jonsson and Burt Kaliski.


Field Summary
private  java.io.ByteArrayOutputStream baos
           
private  int k
           
private  gnu.java.security.util.PRNG prng
          Our default source of randomness.
 
Constructor Summary
private EME_PKCS1_V1_5(int k)
           
 
Method Summary
private  byte[] assembleEM(byte[] PS, byte[] M)
           
 byte[] decode(byte[] EM)
          Separate the encoded message EM into an octet string PS consisting of nonzero octets and a message M as:
 byte[] encode(byte[] M)
          Generates an octet string PS of length k - mLen - 3 consisting of pseudo-randomly generated nonzero octets.
 byte[] encode(byte[] M, gnu.java.security.prng.IRandom irnd)
          Similar to encode(byte[]) 55 method, except that the source of randomness to use for obtaining the padding bytes (an instance of gnu.java.security.prng.IRandom) is given as a parameter.
 byte[] encode(byte[] M, java.util.Random rnd)
          Similar to the encode(byte[], IRandom) 55 method, except that the source of randmoness is an instance of java.util.Random.
static EME_PKCS1_V1_5 getInstance(int k)
           
static EME_PKCS1_V1_5 getInstance(java.security.interfaces.RSAKey key)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

k

private int k

baos

private java.io.ByteArrayOutputStream baos

prng

private gnu.java.security.util.PRNG prng
Our default source of randomness.

Constructor Detail

EME_PKCS1_V1_5

private EME_PKCS1_V1_5(int k)
Method Detail

getInstance

public static final EME_PKCS1_V1_5 getInstance(int k)

getInstance

public static final EME_PKCS1_V1_5 getInstance(java.security.interfaces.RSAKey key)

encode

public byte[] encode(byte[] M)

Generates an octet string PS of length k - mLen - 3 consisting of pseudo-randomly generated nonzero octets. The length of PS will be at least eight octets.

The method then concatenates PS, the message M, and other padding to form an encoded message EM of length k octets as:

    EM = 0x00 || 0x02 || PS || 0x00 || M.
 

This method uses a default PRNG to obtain the padding bytes.


encode

public byte[] encode(byte[] M,
                     gnu.java.security.prng.IRandom irnd)

Similar to encode(byte[]) 55 method, except that the source of randomness to use for obtaining the padding bytes (an instance of gnu.java.security.prng.IRandom) is given as a parameter.


encode

public byte[] encode(byte[] M,
                     java.util.Random rnd)

Similar to the encode(byte[], IRandom) 55 method, except that the source of randmoness is an instance of java.util.Random.


decode

public byte[] decode(byte[] EM)

Separate the encoded message EM into an octet string PS consisting of nonzero octets and a message M as:

    EM = 0x00 || 0x02 || PS || 0x00 || M.
 

If the first octet of EM does not have hexadecimal value 0x00, if the second octet of EM does not have hexadecimal value 0x02, if there is no octet with hexadecimal value 0x00 to separate PS from M, or if the length of PS is less than 8 octets, output "decryption error" and stop.


assembleEM

private byte[] assembleEM(byte[] PS,
                          byte[] M)