Java加密技术(五)——非对称加密算法的由来DH

ming00 2013-11-07

Java非对称加密算法dh

接下来我们分析DH加密算法,一种适基于密钥一致协议的加密算法。

DH

Diffie-Hellman算法(D-H算法),密钥一致协议。是由公开密钥密码体制的奠基人Diffie和Hellman所提出的一种思想。简单的说就是允许两名用户在公开媒体上交换信息以生成"一致"的、可以共享的密钥。换句话说,就是由甲方产出一对密钥(公钥、私钥),乙方依照甲方公钥产生乙方密钥对(公钥、私钥)。以此为基线,作为数据传输保密基础,同时双方使用同一种对称加密算法构建本地密钥(SecretKey)对数据加密。这样,在互通了本地密钥(SecretKey)算法后,甲乙双方公开自己的公钥,使用对方的公钥和刚才产生的私钥加密数据,同时可以使用对方的公钥和自己的私钥对数据解密。不单单是甲乙双方两方,可以扩展为多方共享数据通讯,这样就完成了网络交互数据的安全通讯!该算法源于中国的同余定理——中国馀数定理。

流程分析:

1.甲方构建密钥对儿,将公钥公布给乙方,将私钥保留;双方约定数据加密算法;乙方通过甲方公钥构建密钥对儿,将公钥公布给甲方,将私钥保留。

2.甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥加密数据,发送给乙方加密后的数据;乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥对数据解密。

3.乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥加密数据,发送给甲方加密后的数据;甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥对数据解密。

通过java代码实现如下:Coder类见Java加密技术(一)

Java代码收藏代码

importjava.security.Key;

importjava.security.KeyFactory;

importjava.security.KeyPair;

importjava.security.KeyPairGenerator;

importjava.security.PublicKey;

importjava.security.spec.PKCS8EncodedKeySpec;

importjava.security.spec.X509EncodedKeySpec;

importjava.util.HashMap;

importjava.util.Map;

importjavax.crypto.Cipher;

importjavax.crypto.KeyAgreement;

importjavax.crypto.SecretKey;

importjavax.crypto.interfaces.DHPrivateKey;

importjavax.crypto.interfaces.DHPublicKey;

importjavax.crypto.spec.DHParameterSpec;

/**

*DH安全编码组件

*

*@author梁栋

*@version1.0

*@since1.0

*/

publicabstractclassDHCoderextendsCoder{

publicstaticfinalStringALGORITHM="DH";

/**

*默认密钥字节数

*

*<pre>

*DH

*DefaultKeysize1024

*Keysizemustbeamultipleof64,rangingfrom512to1024(inclusive).

*</pre>

*/

privatestaticfinalintKEY_SIZE=1024;

/**

*DH加密下需要一种对称加密算法对数据加密,这里我们使用DES,也可以使用其他对称加密算法。

*/

publicstaticfinalStringSECRET_ALGORITHM="DES";

privatestaticfinalStringPUBLIC_KEY="DHPublicKey";

privatestaticfinalStringPRIVATE_KEY="DHPrivateKey";

/**

*初始化甲方密钥

*

*@return

*@throwsException

*/

publicstaticMap<String,Object>initKey()throwsException{

KeyPairGeneratorkeyPairGenerator=KeyPairGenerator

.getInstance(ALGORITHM);

keyPairGenerator.initialize(KEY_SIZE);

KeyPairkeyPair=keyPairGenerator.generateKeyPair();

//甲方公钥

DHPublicKeypublicKey=(DHPublicKey)keyPair.getPublic();

//甲方私钥

DHPrivateKeyprivateKey=(DHPrivateKey)keyPair.getPrivate();

Map<String,Object>keyMap=newHashMap<String,Object>(2);

keyMap.put(PUBLIC_KEY,publicKey);

keyMap.put(PRIVATE_KEY,privateKey);

returnkeyMap;

}

/**

*初始化乙方密钥

*

*@paramkey

*甲方公钥

*@return

*@throwsException

*/

publicstaticMap<String,Object>initKey(Stringkey)throwsException{

//解析甲方公钥

byte[]keyBytes=decryptBASE64(key);

X509EncodedKeySpecx509KeySpec=newX509EncodedKeySpec(keyBytes);

KeyFactorykeyFactory=KeyFactory.getInstance(ALGORITHM);

PublicKeypubKey=keyFactory.generatePublic(x509KeySpec);

//由甲方公钥构建乙方密钥

DHParameterSpecdhParamSpec=((DHPublicKey)pubKey).getParams();

KeyPairGeneratorkeyPairGenerator=KeyPairGenerator

.getInstance(keyFactory.getAlgorithm());

keyPairGenerator.initialize(dhParamSpec);

KeyPairkeyPair=keyPairGenerator.generateKeyPair();

//乙方公钥

DHPublicKeypublicKey=(DHPublicKey)keyPair.getPublic();

//乙方私钥

DHPrivateKeyprivateKey=(DHPrivateKey)keyPair.getPrivate();

Map<String,Object>keyMap=newHashMap<String,Object>(2);

keyMap.put(PUBLIC_KEY,publicKey);

keyMap.put(PRIVATE_KEY,privateKey);

returnkeyMap;

}

/**

*加密<br>

*

*@paramdata

*待加密数据

*@parampublicKey

*甲方公钥

*@paramprivateKey

*乙方私钥

*@return

*@throwsException

*/

publicstaticbyte[]encrypt(byte[]data,StringpublicKey,

StringprivateKey)throwsException{

//生成本地密钥

SecretKeysecretKey=getSecretKey(publicKey,privateKey);

//数据加密

Ciphercipher=Cipher.getInstance(secretKey.getAlgorithm());

cipher.init(Cipher.ENCRYPT_MODE,secretKey);

returncipher.doFinal(data);

}

/**

*解密<br>

*

*@paramdata

*待解密数据

*@parampublicKey

*乙方公钥

*@paramprivateKey

*乙方私钥

*@return

*@throwsException

*/

publicstaticbyte[]decrypt(byte[]data,StringpublicKey,

StringprivateKey)throwsException{

//生成本地密钥

SecretKeysecretKey=getSecretKey(publicKey,privateKey);

//数据解密

Ciphercipher=Cipher.getInstance(secretKey.getAlgorithm());

cipher.init(Cipher.DECRYPT_MODE,secretKey);

returncipher.doFinal(data);

}

/**

*构建密钥

*

*@parampublicKey

*公钥

*@paramprivateKey

*私钥

*@return

*@throwsException

*/

privatestaticSecretKeygetSecretKey(StringpublicKey,StringprivateKey)

throwsException{

//初始化公钥

byte[]pubKeyBytes=decryptBASE64(publicKey);

KeyFactorykeyFactory=KeyFactory.getInstance(ALGORITHM);

X509EncodedKeySpecx509KeySpec=newX509EncodedKeySpec(pubKeyBytes);

PublicKeypubKey=keyFactory.generatePublic(x509KeySpec);

//初始化私钥

byte[]priKeyBytes=decryptBASE64(privateKey);

PKCS8EncodedKeySpecpkcs8KeySpec=newPKCS8EncodedKeySpec(priKeyBytes);

KeypriKey=keyFactory.generatePrivate(pkcs8KeySpec);

KeyAgreementkeyAgree=KeyAgreement.getInstance(keyFactory

.getAlgorithm());

keyAgree.init(priKey);

keyAgree.doPhase(pubKey,true);

//生成本地密钥

SecretKeysecretKey=keyAgree.generateSecret(SECRET_ALGORITHM);

returnsecretKey;

}

/**

*取得私钥

*

*@paramkeyMap

*@return

*@throwsException

*/

publicstaticStringgetPrivateKey(Map<String,Object>keyMap)

throwsException{

Keykey=(Key)keyMap.get(PRIVATE_KEY);

returnencryptBASE64(key.getEncoded());

}

/**

*取得公钥

*

*@paramkeyMap

*@return

*@throwsException

*/

publicstaticStringgetPublicKey(Map<String,Object>keyMap)

throwsException{

Keykey=(Key)keyMap.get(PUBLIC_KEY);

returnencryptBASE64(key.getEncoded());

}

}

再给出一个测试类:

Java代码收藏代码

importstaticorg.junit.Assert.*;

importjava.util.Map;

importorg.junit.Test;

/**

*

*@author梁栋

*@version1.0

*@since1.0

*/

publicclassDHCoderTest{

@Test

publicvoidtest()throwsException{

//生成甲方密钥对儿

Map<String,Object>aKeyMap=DHCoder.initKey();

StringaPublicKey=DHCoder.getPublicKey(aKeyMap);

StringaPrivateKey=DHCoder.getPrivateKey(aKeyMap);

System.err.println("甲方公钥:\r"+aPublicKey);

System.err.println("甲方私钥:\r"+aPrivateKey);

//由甲方公钥产生本地密钥对儿

Map<String,Object>bKeyMap=DHCoder.initKey(aPublicKey);

StringbPublicKey=DHCoder.getPublicKey(bKeyMap);

StringbPrivateKey=DHCoder.getPrivateKey(bKeyMap);

System.err.println("乙方公钥:\r"+bPublicKey);

System.err.println("乙方私钥:\r"+bPrivateKey);

StringaInput="abc";

System.err.println("原文:"+aInput);

//由甲方公钥,乙方私钥构建密文

byte[]aCode=DHCoder.encrypt(aInput.getBytes(),aPublicKey,

bPrivateKey);

//由乙方公钥,甲方私钥解密

byte[]aDecode=DHCoder.decrypt(aCode,bPublicKey,aPrivateKey);

StringaOutput=(newString(aDecode));

System.err.println("解密:"+aOutput);

assertEquals(aInput,aOutput);

System.err.println("===============反过来加密解密==================");

StringbInput="def";

System.err.println("原文:"+bInput);

//由乙方公钥,甲方私钥构建密文

byte[]bCode=DHCoder.encrypt(bInput.getBytes(),bPublicKey,

aPrivateKey);

//由甲方公钥,乙方私钥解密

byte[]bDecode=DHCoder.decrypt(bCode,aPublicKey,bPrivateKey);

StringbOutput=(newString(bDecode));

System.err.println("解密:"+bOutput);

assertEquals(bInput,bOutput);

}

}

控制台输出:

Console代码收藏代码

甲方公钥:

MIHfMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYXrgHz

W5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpDTWSG

kx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgANDAAJAdAWBVmIzqcko

Ej6qFjLDL2+Y3FPq1iRbnOyOpDj71yKaK1K+FhTv04B0zy4DKcvAASV7/Gv0W+bgqdmffRkqrQ==

甲方私钥:

MIHRAgEAMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYX

rgHzW5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpD

TWSGkx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgAQyAjACJRfy1LyR

eHyD+4Hfb+xR0uoIGR1oL9i9Nk6g2AAuaDPgEVWHn+QXID13yL/uDos=

乙方公钥:

MIHfMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYXrgHz

W5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpDTWSG

kx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgANDAAJAVEYSfBA+I9nr

dWw3OBv475C+eBrWBBYqt0m6/eu4ptuDQHwV4MmUtKAC2wc2nNrdb1wmBhY1X8RnWkJ1XmdDbQ==

乙方私钥:

MIHSAgEAMIGXBgkqhkiG9w0BAwEwgYkCQQD8poLOjhLKuibvzPcRDlJtsHiwXt7LzR60ogjzrhYX

rgHzW5Gkfm32NBPF4S7QiZvNEyrNUNmRUb3EPuc3WS4XAkBnhHGyepz0TukaScUUfbGpqvJE8FpD

TWSGkx0tFCcbnjUDC3H9c9oXkGmzLik1Yw4cIGI1TQ2iCmxBblC+eUykAgIBgAQzAjEAqaZiCdXp

2iNpdBlHRaO9ir70wo2n32xNlIzIX19VLSPCDdeUWkgRv4CEj/8k+/yd

原文:abc

解密:abc

===============反过来加密解密==================

原文:def

解密:def

如我所言,甲乙双方在获得对方公钥后可以对发送给对方的数据加密,同时也能对接收到的数据解密,达到了数据安全通信的目的!

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