SymmetricEncryption.java
/*
** Module : SymmetricEncryption.java
** Abstract : A symmetric algorithm used for making strings (passwords) not so easy readable.
**
** Copyright (c) 2015-2023, Golden Code Development Corporation.
**
** -#- -I- --Date-- ---------------------------------Description---------------------------------
** 001 OM 20151113 Initial implementation.
** 002 EVL 20160406 Javadoc fix.
** 003 GBB 20230512 Logging methods replaced by CentralLogger/ConversionStatus.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
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** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
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**
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*/
package com.goldencode.p2j.security;
import com.goldencode.p2j.util.logging.*;
/**
* Utility class that mimics the symmetric encryption of Progress' {@code genpassword} utility.
* The algorithm used is quite naive, each byte of the message is XOR-ed with the corresponding
* byte of a <i>secret</i> key. If the key is shorter, its pointer is restarted from the beginning
* and the process continues until the entire message is processed. Evidently, applying this
* algorithm twice using the same password/key we obtain the original message:
* <pre>(a XOR b) XOR b = a</pre>
* <p>
* The difference between the format of encrypted and plain message occurs because the encrypted
* message, in the initial form can contain non-printable ascii codes. So it is converted to a
* hexadecimal representation, which uses twice as many characters but they are limited to
* hexadecimal digits.
*/
public class SymmetricEncryption
{
/** The key used for encrypting and decrypting the message. */
private static final String SYM_KEY = "PROGRESS";
/** Logger */
private static final CentralLogger LOG = CentralLogger.get(SymmetricEncryption.class);
/**
* The command-line utility. The syntax is:
* <pre>
* > java SymmetricEncryption plain [coded]
* </pre>
* If only {@code plain} is provided, then the argument is encrypted with symmetric algorithm
* and the result is printed to STDOUT.
* <p>
* If the 2nd parameter is also provided ({@code coded}) then it is used for verification
* (against the encrypted {@code plain}). On success, the application returns normally without
* printing anything. Otherwise a message is printed to STDERR and -2 is returned to OS.
*
* @param args
* The parameters passed in by OS.
*/
public static void main(String[] args)
{
if (args.length == 0)
{
LOG.severe("At least a parameter must be provided.");
System.exit(-1);
}
if (args.length == 1)
{
LOG.info(encrypt(args[0]));
return;
}
if (args.length == 2)
{
if (encrypt(args[0]).equalsIgnoreCase(args[1]))
{
// 1st argument encrypted equals 2nd one
return;
}
// if testing fails, return an error level to OS
LOG.severe("The plain and coded do not match.");
System.exit(-2);
}
// max 2 parameter may be passed in
LOG.severe("Too many parameters.");
System.exit(-3);
}
/**
* Encryption method. The symmetric encryption is performed on input string and the result is
* returned. Because the intermediary code is not usually printable, the final result is
* passed through a hex encoder.
*
* @param plainMessage
* The message to be encoded in plain ASCII.
*
* @return The encrypted message. It is always twice as long and the characters are
* hexadecimal digits.
*/
public static String encrypt(String plainMessage)
{
if (plainMessage == null || plainMessage.length() == 0)
{
return plainMessage;
}
return toHexString(process(SYM_KEY, plainMessage.getBytes()));
}
/**
* Decryption method. The symmetric crypt algorithm is applied again so the original message
* is obtained.
*
* @param codedMessage
* The encoded message. Since it is hex-encoded, its size must be even and each
* character a hexadecimal digit.
*
* @return The original message.
*/
public static String decrypt(String codedMessage)
{
if (codedMessage == null || codedMessage.length() == 0)
{
return codedMessage;
}
return new String(process(SYM_KEY, asBytes(codedMessage)));
}
/**
* Utility method. Converts a byte array to its ASCII printable string representation using
* hexadecimal encoding of each byte.
*
* @param code
* An array of bytes to be processed. In this case this is the encrypted message.
*
* @return Hexadecimal representation of the {@code code}.
*/
private static String toHexString(byte[] code)
{
// allocate the exact space for hexadecimal representation of the code array
StringBuilder sb = new StringBuilder(code.length * 2);
for (byte aByte : code)
{
// insert a leading 0 to keep the 2 digits per byte for 1 digit representation
if ((aByte & 255) < 16)
{
sb.append("0");
}
sb.append(Long.toString((long) (aByte & 255), 16));
}
return sb.toString();
}
/**
* Converts a hexadecimal representation to initial bytes array.
*
* @param hexString
* The input string. Must have an even length and all characters be valid hexadecimal
* digits.
*
* @return The original byte array.
*/
private static byte[] asBytes(String hexString)
{
int len = hexString.length();
byte[] bytes = new byte[((len & 1) == 0) ? (len / 2) : len];
int i = 0;
for (int j = 0; i < len; ++j)
{
// take 2 hex digits and generate a single byte
short var7 = Short.parseShort(hexString.substring(i, i + 2), 16);
bytes[j] = (byte)(var7 & 255);
i += 2;
}
return bytes;
}
/**
* This is the core algorithm. It is applied for both encrypting and decrypting the message.
* The {@code passwd} is transformed into a byte array, then the message is linearly processed:
* each byte is XOR-ed with the corresponding byte from the key.
*
* @param passwd
* The password / key used for coding.
* @param data
* The data to be processed.
*
* @return The processed array.
*/
private static byte[] process(String passwd, byte[] data)
{
byte[] kData = passwd.getBytes();
byte[] pData = new byte[data.length];
for (int i = 0, j = 0; i < data.length; ++j)
{
if (j >= kData.length)
{
// if we got to end of key, we roll it back from the beginning
j = 0;
}
pData[i] = (byte)(data[i] ^ kData[j]);
++i;
}
return pData;
}
}