详解DES加密算法及在Java程序中的使用示例
DES加密算法
DES全称为DataEncryptionStandard，即数据加密标准，是一种使用密钥加密的块算法，1976年被美国联邦政府的国家标准局确定为联邦资料处理标准（FIPS），随后在国际上广泛流传开来。
DES算法的入口参数有三个:Key、Data、Mode。其中Key为7个字节共56位,是DES算法的工作密钥;Data为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。
DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是56位，其算法主要分为两步：
1）初始置换
其功能是把输入的64位数据块按位重新组合,并把输出分为L0、R0两部分,每部分各长32位,其置换规则为将输入的第58位换到第一位,第50位换到第2位……依此类推,最后一位是原来的第7位。L0、R0则是换位输出后的两部分，L0是输出的左32位,R0是右32位,例:设置换前的输入值为D1D2D3……D64,则经过初始置换后的结果为:L0=D58D50……D8;R0=D57D49……D7。
其置换规则见下表：
58,50,42,34,26,18,10,2,60,52,44,36,28,20,12,4, 62,54,46,38,30,22,14,6,64,56,48,40,32,24,16,8, 57,49,41,33,25,17,9,1,59,51,43,35,27,19,11,3, 61,53,45,37,29,21,13,5,63,55,47,39,31,23,15,7,
2）逆置换
经过16次迭代运算后,得到L16、R16,将此作为输入,进行逆置换,逆置换正好是初始置换的逆运算，由此即得到密文输出。
此算法是对称加密算法体系中的代表,在计算机网络系统中广泛使用.
Java基本实现
packagecom.stone.security;
importjava.security.Key;
importjava.security.SecureRandom;
importjavax.crypto.Cipher;
importjavax.crypto.KeyGenerator;
importjavax.crypto.SecretKey;
importjavax.crypto.SecretKeyFactory;
importjavax.crypto.spec.DESKeySpec;
importjavax.crypto.spec.IvParameterSpec;
/**
*DES算法1972美国IBM研制，对称加密算法
*/
publicclassDES{
//算法名称
publicstaticfinalStringKEY_ALGORITHM="DES";
//算法名称/加密模式/填充方式
publicstaticfinalStringCIPHER_ALGORITHM_ECB="DES/ECB/PKCS5Padding";
publicstaticfinalStringCIPHER_ALGORITHM_CBC="DES/CBC/PKCS5Padding";
publicstaticvoidmain(String[]args)throwsException{
/*
*使用ECBmode
*密钥生成器生成密钥
*ECBmodecannotuseIV
*/
byte[]key=generateKey();
byte[]encrypt=encrypt("胃炎F#*（x）".getBytes(),key);
System.out.println(newString(decrypt(encrypt,key)));
/*
*使用CBCmode
*使用密钥工厂生成密钥，加密解密
*iv:DESinCBCmodeandRSAcipherswithOAEPencodingoperation.
*/
DESKeySpecdks=newDESKeySpec(generateKey());
SecretKeyFactoryfactory=SecretKeyFactory.getInstance(KEY_ALGORITHM);
SecretKeysecretKey=factory.generateSecret(dks);
Ciphercipher=Cipher.getInstance(CIPHER_ALGORITHM_CBC);
cipher.init(Cipher.ENCRYPT_MODE,secretKey,newIvParameterSpec(getIV()));
byte[]enc=cipher.doFinal("胃炎A%F#*（x）".getBytes());//加密
cipher.init(Cipher.DECRYPT_MODE,secretKey,newIvParameterSpec(getIV()));
byte[]dec=cipher.doFinal(enc);//解密
System.out.println(newString(dec));
}
staticbyte[]getIV(){
Stringiv="asdfivh7";//IVlength:mustbe8byteslong
returniv.getBytes();
}
/**
*生成密钥
*
*@return
*@throwsException
*/
privatestaticbyte[]generateKey()throwsException{
KeyGeneratorkeyGenerator=KeyGenerator.getInstance(KEY_ALGORITHM);
keyGenerator.init(56);//des必须是56,此初始方法不必须调用
SecretKeysecretKey=keyGenerator.generateKey();
returnsecretKey.getEncoded();
}
/**
*还原密钥
*
*@paramkey
*@return
*@throwsException
*/
privatestaticKeytoKey(byte[]key)throwsException{
DESKeySpecdes=newDESKeySpec(key);
SecretKeyFactorykeyFactory=SecretKeyFactory.getInstance(KEY_ALGORITHM);
SecretKeysecretKey=keyFactory.generateSecret(des);
returnsecretKey;
}
/**
*加密
*@paramdata原文
*@paramkey
*@return密文
*@throwsException
*/
publicstaticbyte[]encrypt(byte[]data,byte[]key)throwsException{
Keyk=toKey(key);
Ciphercipher=Cipher.getInstance(CIPHER_ALGORITHM_ECB);
cipher.init(Cipher.ENCRYPT_MODE,k,newSecureRandom());
returncipher.doFinal(data);
}
/**
*解密
*@paramdata密文
*@paramkey
*@return明文、原文
*@throwsException
*/
publicstaticbyte[]decrypt(byte[]data,byte[]key)throwsException{
Keyk=toKey(key);
Ciphercipher=Cipher.getInstance(CIPHER_ALGORITHM_ECB);
cipher.init(Cipher.DECRYPT_MODE,k,newSecureRandom());
returncipher.doFinal(data);
}
}
Java三重DES实现：
packagecom.stone.security;
importjavax.crypto.Cipher;
importjavax.crypto.KeyGenerator;
importjavax.crypto.SecretKey;
importjavax.crypto.SecretKeyFactory;
importjavax.crypto.spec.DESedeKeySpec;
importjavax.crypto.spec.IvParameterSpec;
/**
*三重加密3DES也作TripleDES,
*/
publicclassTripleDES{
//算法名称
publicstaticfinalStringKEY_ALGORITHM="DESede";
//算法名称/加密模式/填充方式
publicstaticfinalStringCIPHER_ALGORITHM_ECB="DESede/ECB/PKCS5Padding";
publicstaticfinalStringCIPHER_ALGORITHM_CBC="DESede/CBC/PKCS5Padding";
privateKeyGeneratorkeyGen;
privateSecretKeysecretKey;
privateSecretKeysecretKey2;
privateCiphercipher;
privatestaticbyte[]encryptData;
publicstaticvoidmain(String[]args)throwsException{
TripleDEStripleDES=newTripleDES("ECB");
tripleDES.encrypt("sau8jzxlcvm,'123`98(*^&%^^JCBZX>>A<S<}}{");
System.out.println("加密后："+newString(encryptData));
System.out.println("解密后："+newString(tripleDES.decrypt(encryptData)));
tripleDES=newTripleDES("CBC");
tripleDES.encrypt2("sau8jzxlcDQV#><«|vm,'123`98(*^&%^^JCBZX>>A<S<}}{");
System.out.println("加密后："+newString(encryptData));
System.out.println("解密后："+newString(tripleDES.decrypt2(encryptData)));
}
publicTripleDES(Stringmode)throwsException{
if("ECB".equals(mode)){
//cipher=Cipher.getInstance(KEY_ALGORITHM);
cipher=Cipher.getInstance(CIPHER_ALGORITHM_ECB);
keyGen=KeyGenerator.getInstance(KEY_ALGORITHM);
secretKey=keyGen.generateKey();
}elseif("CBC".equals(mode)){
cipher=Cipher.getInstance(CIPHER_ALGORITHM_CBC);
keyGen=KeyGenerator.getInstance(KEY_ALGORITHM);
DESedeKeySpecspec=newDESedeKeySpec(keyGen.generateKey().getEncoded());
secretKey2=SecretKeyFactory.getInstance(KEY_ALGORITHM).generateSecret(spec);
}
}
/**
*加密
*@paramstr
*@return
*@throwsException
*/
publicbyte[]encrypt(Stringstr)throwsException{
cipher.init(Cipher.ENCRYPT_MODE,secretKey);
returnencryptData=cipher.doFinal(str.getBytes());
}
/**
*解密
*@paramencrypt
*@return
*@throwsException
*/
publicbyte[]decrypt(byte[]encrypt)throwsException{
cipher.init(Cipher.DECRYPT_MODE,secretKey);
returnencryptData=cipher.doFinal(encrypt);
}
byte[]getIV(){
return"administ".getBytes();
}
/**
*加密
*@paramstr
*@return
*@throwsException
*/
publicbyte[]encrypt2(Stringstr)throwsException{
cipher.init(Cipher.ENCRYPT_MODE,secretKey2,newIvParameterSpec(getIV()));
returnencryptData=cipher.doFinal(str.getBytes());
}
/**
*解密
*@paramencrypt
*@return
*@throwsException
*/
publicbyte[]decrypt2(byte[]encrypt)throwsException{
cipher.init(Cipher.DECRYPT_MODE,secretKey2,newIvParameterSpec(getIV()));
returnencryptData=cipher.doFinal(encrypt);
}
}