Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free.
I'm working on a project that requires 3DES encryption in Java. The issue is that I've been (and will continue to be) supplied with a 128-bit hex key like "ABCDEFABCDEF". Conversion to bytes is no issue. What is the issue, however, is that the Java Cryptographic Extensions API will choke on this key, saying it is invalid. I gather that the MSB of each byte is merely a parity bit, so the JCE expects me to remove those (or so I think). In .NET, however, I can specify the key as supplied, and it quietly handles the encryption/decryption with no complaints.
Is there any way I can generate the kind of key the JCE expects from the kind of key I'm supplied?
I've found that the JCE allows you specify an 8-byte key for DES encryption, so I tried implementing 3DES as DES EDE using half of the supplied key. However, I'm still getting inconsistent results with .NET.
Here's the Java code:
import javax.crypto.C
import javax.crypto.SecretK
import javax.crypto.spec.SecretKeyS
import javax.crypto.spec.IvParameterS
public class Main{
public static void main(String[] args) throws Exception {
byte [] plain = "I eat fish every day".getBytes("utf-8");
byte [] keyBytes = new byte [] { (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00
byte [] key2Bytes = new byte [] { (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x0
}; // actual keys replaced with dummies.
SecretKey keySpec = new SecretKeySpec(keyBytes, "DES");
SecretKey keySpec2 = new SecretKeySpec(key2Bytes, "DES");
IvParameterSpec iv = new IvParameterSpec(new byte[8]);
Cipher e_cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
Cipher cipher = Cipher.getInstance("DES/CBC/NoPadding");
e_cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);
cipher.init(Cipher.DECRYPT_MODE, keySpec2, iv);
byte [] cipherText = e_cipher.doFinal(plain);
cipherText = cipher.doFinal(cipherText);
cipherText = e_cipher.doFinal(cipherText);
System.out.println("Ciphertext: " + new sun.misc.BASE64Encoder().encode(cipherText));
and here's the .NET code:
using System.IO;
using System.Security.C
using System.T
namespace EncryptionDemo
class Program
public static void Main(string[] args)
Console.WriteLine("Hello World!");
// TODO: Implement Functionality Here
var plainBytes = Encoding.UTF8.GetBytes("I eat fish every day");
var keyBytes = new byte [] { 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00
var tripleDES = TripleDESCryptoServiceProvider.Create();
var transform = tripleDES.CreateEncryptor(keyBytes, new byte [8]);
var memStream = new MemoryStream();
var cStream = new CryptoStream(memStream, transform, CryptoStreamMode.Write);
cStream.Write(plainBytes, 0, plainBytes.Length);
cStream.FlushFinalBlock();
//memStream.Position = 0;
var cipherBytes = memStream.ToArray();
Console.WriteLine("Ciphertext: " + Convert.ToBase64String(cipherBytes));
Console.Write("Press any key to continue . . . ");
Console.ReadKey(true);
Both produce different outputs (some characters in the Base64 string are the same)
the Sun provider doesn't accept 16-byte 3DES keys, but the BouncyCastle provider does. I just tried it out and it works like a charm - it produces the same output as the .NET code!
import javax.crypto.C
import javax.crypto.SecretK
import javax.crypto.spec.SecretKeyS
import javax.crypto.spec.IvParameterS
import java.security.S
import org.bouncycastle.jce.provider.BouncyCastleP
public class Main{
public static void main(String[] args) throws Exception {
Security.addProvider(new BouncyCastleProvider());
byte [] plain = "I eat fish every day".getBytes("utf-8");
byte [] keyBytes = new byte [] { (byte) 0xC1, (byte) 0x57, (byte) 0x45, (byte) 0x08,
(byte) 0x85, (byte) 0x02, (byte) 0xB0, (byte) 0xD3,
(byte) 0xA2, (byte) 0xEF, (byte) 0x68, (byte) 0x43,
(byte) 0x5E, (byte) 0xE6, (byte) 0xD0, (byte) 0x75 };
SecretKey keySpec = new SecretKeySpec(keyBytes, "DESede");
IvParameterSpec iv = new IvParameterSpec(new byte[8]);
Cipher e_cipher = Cipher.getInstance("DESede/CBC/PKCS5Padding", "BC");
e_cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);
byte [] cipherText = e_cipher.doFinal(plain);
System.out.println("Ciphertext: " + new sun.misc.BASE64Encoder().encode(cipherText));
3DES keys are 192 bits long.
How are you creating the SecretKey instance? What error message to you get?
The Java code in your question is using DES, not "Triple DES". The algorithm name should be "DESede/CBC/PKCS5Padding". The code in your answer probably works because you got the algorithm right, not because you switched providers. The SunJCE provider in Java 6 will accept 128-bit keys (and use keying option 2). I am not sure about older versions.
155k32241347
project, the problem is worked around by always using either single-length (8-byte) or triple-length (24-byte) keys. Let's say your clear double-length key (in bytes) is AAAAAAAA BBBBBBBB. All code in the jPOS project I've seen so far that uses the JCE appends the first 8 bytes again to the clear key, so it becomes a triple-length key as such: AAAAAAAA BBBBBBBB AAAAAAAA. It seems the Sun provider does accept this material for creating a SecreKeySpec, as it is 192 bits long, as @erickson mentioned.
Your Answer
Sign up or
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Post as a guest
By posting your answer, you agree to the
Not the answer you're looking for?
Browse other questions tagged
Stack Overflow works best with JavaScript enabled数学题aaaa已知三角形ABC的重心为G（即三角形的三条中线的交点）,又E.F分别是BC,CA的中点,若三角形ABC的面积为m,求三角形EGF的面积._百度作业帮
数学题aaaa已知三角形ABC的重心为G（即三角形的三条中线的交点）,又E.F分别是BC,CA的中点,若三角形ABC的面积为m,求三角形EGF的面积.
数学题aaaa已知三角形ABC的重心为G（即三角形的三条中线的交点）,又E.F分别是BC,CA的中点,若三角形ABC的面积为m,求三角形EGF的面积.
E.F分别是BC,CA的中点所以 BC ‖CA 根据相似三角形可得：EF=1/2AB连接CG交AB于D,重心为G,所以：CG=2GD（重心性质）由BC ‖CA ,相似三角形可得：对应边上的高也成比例.所以：EF上的高是AB上的高的1/6所以三角形EGF面积=1/2*1/6 *S△ABC=1/12m
m/12如果你知道重心分中线的比是1:2的话,这题应该就不难了
做CH交AB于点H，交EF于点O，所以三角形ABC面积为1/2AB×CH=m而EF=1/2AB，CO=OH，GH=1/3CH所以OG=CH-GH-OC=CH-1/3CH-1/2CH=1/6CH所以三角形EGF的面积为：1/2×EF×OG=1/2×1/2AB×1/6GH=1/12m}