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gnu.java.security.sig.rsa

Class EME_PKCS1_V1_5

public class EME_PKCS1_V1_5
extends 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.

Method Summary

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.
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, IRandom irnd)
Similar to encode(byte[]) method, except that the source of randomness to use for obtaining the padding bytes (an instance of IRandom) is given as a parameter.
byte[]
encode(byte[] M, Random rnd)
Similar to the encode(byte[],IRandom) method, except that the source of randmoness is an instance of Random.
static EME_PKCS1_V1_5
getInstance(int k)
static EME_PKCS1_V1_5
getInstance(RSAKey key)

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

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.

Parameters:
EM - the designated encoded message.
Returns:
the decoded message M framed in the designated EM value.
Throws:
IllegalArgumentException - if the length of the designated entity EM is different than k (the length in bytes of the public shared modulus), or if any of the conditions described above is detected.

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.

Parameters:
M - the message to encode.
Returns:
the encoded message EM.

encode

public byte[] encode(byte[] M,
                     IRandom irnd)
Similar to encode(byte[]) method, except that the source of randomness to use for obtaining the padding bytes (an instance of IRandom) is given as a parameter.
Parameters:
M - the message to encode.
irnd - the IRandom instance to use as a source of randomness.
Returns:
the encoded message EM.

encode

public byte[] encode(byte[] M,
                     Random rnd)
Similar to the encode(byte[],IRandom) method, except that the source of randmoness is an instance of Random.
Parameters:
M - the message to encode.
rnd - the Random instance to use as a source of randomness.
Returns:
the encoded message EM.

getInstance

public static final EME_PKCS1_V1_5 getInstance(int k)

getInstance

public static final EME_PKCS1_V1_5 getInstance(RSAKey key)
EME_PKCS1_V1_5.java -- Copyright (C) 2003, 2006 Free Software Foundation, Inc. This file is a part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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