該工具類中用到了BASE64，需要借助第三方類庫：javabase64-1.3.1.jar注意：RSA加密明文最大長度117字節，解密要求密文最大長度為128字節，所以在加密和解密的過程中需要分塊進行。

RSA加密對明文的長度是有限制的，如果加密數據過大會拋出如下異常：Exception?in?thread?"main"?javax.crypto.IllegalBlockSizeException:?Data?must?not?be?longer?than?117?bytes

at?com.sun.crypto.provider.RSACipher.a(DashoA13*..)

at?com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..)

at?javax.crypto.Cipher.doFinal(DashoA13*..)

RSAUtils.javapackage?security;

import?java.io.ByteArrayOutputStream;

import?java.security.Key;

import?java.security.KeyFactory;

import?java.security.KeyPair;

import?java.security.KeyPairGenerator;

import?java.security.PrivateKey;

import?java.security.PublicKey;

import?java.security.Signature;

import?java.security.interfaces.RSAPrivateKey;

import?java.security.interfaces.RSAPublicKey;

import?java.security.spec.PKCS8EncodedKeySpec;

import?java.security.spec.X509EncodedKeySpec;

import?java.util.HashMap;

import?java.util.Map;

import?javax.crypto.Cipher;

/**

*?

*?RSA公鑰/私鑰/簽名工具包

*?

*?

*?羅納德·李維斯特(Ron?[R]ivest)、阿迪·薩莫爾(Adi?[S]hamir)和倫納德·阿德曼(Leonard?[A]dleman)

*?

*?

*?字符串格式的密鑰在未在特殊說明情況下都為BASE64編碼格式

*?由于非對稱加密速度極其緩慢，一般文件不使用它來加密而是使用對稱加密，

*?非對稱加密算法可以用來對對稱加密的密鑰加密，這樣保證密鑰的安全也就保證了數據的安全

*?

*

*?@author?IceWee

*?@date?2012-4-26

*?@version?1.0

*/

public?class?RSAUtils?{

/**

*?加密算法RSA

*/

public?static?final?String?KEY_ALGORITHM?=?"RSA";

/**

*?簽名算法

*/

public?static?final?String?SIGNATURE_ALGORITHM?=?"MD5withRSA";

/**

*?獲取公鑰的key

*/

private?static?final?String?PUBLIC_KEY?=?"RSAPublicKey";

/**

*?獲取私鑰的key

*/

private?static?final?String?PRIVATE_KEY?=?"RSAPrivateKey";

/**

*?RSA最大加密明文大小

*/

private?static?final?int?MAX_ENCRYPT_BLOCK?=?117;

/**

*?RSA最大解密密文大小

*/

private?static?final?int?MAX_DECRYPT_BLOCK?=?128;

/**

*?

*?生成密鑰對(公鑰和私鑰)

*?

*

*?@return

*?@throws?Exception

*/

public?static?Map?genKeyPair()?throws?Exception?{

KeyPairGenerator?keyPairGen?=?KeyPairGenerator.getInstance(KEY_ALGORITHM);

keyPairGen.initialize(1024);

KeyPair?keyPair?=?keyPairGen.generateKeyPair();

RSAPublicKey?publicKey?=?(RSAPublicKey)?keyPair.getPublic();

RSAPrivateKey?privateKey?=?(RSAPrivateKey)?keyPair.getPrivate();

Map?keyMap?=?new?HashMap(2);

keyMap.put(PUBLIC_KEY,?publicKey);

keyMap.put(PRIVATE_KEY,?privateKey);

return?keyMap;

}

/**

*?

*?用私鑰對信息生成數字簽名

*?

*

*?@param?data?已加密數據

*?@param?privateKey?私鑰(BASE64編碼)

*

*?@return

*?@throws?Exception

*/

public?static?String?sign(byte[]?data,?String?privateKey)?throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(privateKey);

PKCS8EncodedKeySpec?pkcs8KeySpec?=?new?PKCS8EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

PrivateKey?privateK?=?keyFactory.generatePrivate(pkcs8KeySpec);

Signature?signature?=?Signature.getInstance(SIGNATURE_ALGORITHM);

signature.initSign(privateK);

signature.update(data);

return?Base64Utils.encode(signature.sign());

}

/**

*?

*?校驗數字簽名

*?

*

*?@param?data?已加密數據

*?@param?publicKey?公鑰(BASE64編碼)

*?@param?sign?數字簽名

*

*?@return

*?@throws?Exception

*

*/

public?static?boolean?verify(byte[]?data,?String?publicKey,?String?sign)

throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(publicKey);

X509EncodedKeySpec?keySpec?=?new?X509EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

PublicKey?publicK?=?keyFactory.generatePublic(keySpec);

Signature?signature?=?Signature.getInstance(SIGNATURE_ALGORITHM);

signature.initVerify(publicK);

signature.update(data);

return?signature.verify(Base64Utils.decode(sign));

}

/**

*?

*?私鑰解密

*?

*

*?@param?encryptedData?已加密數據

*?@param?privateKey?私鑰(BASE64編碼)

*?@return

*?@throws?Exception

*/

public?static?byte[]?decryptByPrivateKey(byte[]?encryptedData,?String?privateKey)

throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(privateKey);

PKCS8EncodedKeySpec?pkcs8KeySpec?=?new?PKCS8EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

Key?privateK?=?keyFactory.generatePrivate(pkcs8KeySpec);

Cipher?cipher?=?Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.DECRYPT_MODE,?privateK);

int?inputLen?=?encryptedData.length;

ByteArrayOutputStream?out?=?new?ByteArrayOutputStream();

int?offSet?=?0;

byte[]?cache;

int?i?=?0;

//?對數據分段解密

while?(inputLen?-?offSet?>?0)?{

if?(inputLen?-?offSet?>?MAX_DECRYPT_BLOCK)?{

cache?=?cipher.doFinal(encryptedData,?offSet,?MAX_DECRYPT_BLOCK);

}?else?{

cache?=?cipher.doFinal(encryptedData,?offSet,?inputLen?-?offSet);

}

out.write(cache,?0,?cache.length);

i++;

offSet?=?i?*?MAX_DECRYPT_BLOCK;

}

byte[]?decryptedData?=?out.toByteArray();

out.close();

return?decryptedData;

}

/**

*?

*?公鑰解密

*?

*

*?@param?encryptedData?已加密數據

*?@param?publicKey?公鑰(BASE64編碼)

*?@return

*?@throws?Exception

*/

public?static?byte[]?decryptByPublicKey(byte[]?encryptedData,?String?publicKey)

throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(publicKey);

X509EncodedKeySpec?x509KeySpec?=?new?X509EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

Key?publicK?=?keyFactory.generatePublic(x509KeySpec);

Cipher?cipher?=?Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.DECRYPT_MODE,?publicK);

int?inputLen?=?encryptedData.length;

ByteArrayOutputStream?out?=?new?ByteArrayOutputStream();

int?offSet?=?0;

byte[]?cache;

int?i?=?0;

//?對數據分段解密

while?(inputLen?-?offSet?>?0)?{

if?(inputLen?-?offSet?>?MAX_DECRYPT_BLOCK)?{

cache?=?cipher.doFinal(encryptedData,?offSet,?MAX_DECRYPT_BLOCK);

}?else?{

cache?=?cipher.doFinal(encryptedData,?offSet,?inputLen?-?offSet);

}

out.write(cache,?0,?cache.length);

i++;

offSet?=?i?*?MAX_DECRYPT_BLOCK;

}

byte[]?decryptedData?=?out.toByteArray();

out.close();

return?decryptedData;

}

/**

*?

*?公鑰加密

*?

*

*?@param?data?源數據

*?@param?publicKey?公鑰(BASE64編碼)

*?@return

*?@throws?Exception

*/

public?static?byte[]?encryptByPublicKey(byte[]?data,?String?publicKey)

throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(publicKey);

X509EncodedKeySpec?x509KeySpec?=?new?X509EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

Key?publicK?=?keyFactory.generatePublic(x509KeySpec);

//?對數據加密

Cipher?cipher?=?Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.ENCRYPT_MODE,?publicK);

int?inputLen?=?data.length;

ByteArrayOutputStream?out?=?new?ByteArrayOutputStream();

int?offSet?=?0;

byte[]?cache;

int?i?=?0;

//?對數據分段加密

while?(inputLen?-?offSet?>?0)?{

if?(inputLen?-?offSet?>?MAX_ENCRYPT_BLOCK)?{

cache?=?cipher.doFinal(data,?offSet,?MAX_ENCRYPT_BLOCK);

}?else?{

cache?=?cipher.doFinal(data,?offSet,?inputLen?-?offSet);

}

out.write(cache,?0,?cache.length);

i++;

offSet?=?i?*?MAX_ENCRYPT_BLOCK;

}

byte[]?encryptedData?=?out.toByteArray();

out.close();

return?encryptedData;

}

/**

*?

*?私鑰加密

*?

*

*?@param?data?源數據

*?@param?privateKey?私鑰(BASE64編碼)

*?@return

*?@throws?Exception

*/

public?static?byte[]?encryptByPrivateKey(byte[]?data,?String?privateKey)

throws?Exception?{

byte[]?keyBytes?=?Base64Utils.decode(privateKey);

PKCS8EncodedKeySpec?pkcs8KeySpec?=?new?PKCS8EncodedKeySpec(keyBytes);

KeyFactory?keyFactory?=?KeyFactory.getInstance(KEY_ALGORITHM);

Key?privateK?=?keyFactory.generatePrivate(pkcs8KeySpec);

Cipher?cipher?=?Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.ENCRYPT_MODE,?privateK);

int?inputLen?=?data.length;

ByteArrayOutputStream?out?=?new?ByteArrayOutputStream();

int?offSet?=?0;

byte[]?cache;

int?i?=?0;

//?對數據分段加密

while?(inputLen?-?offSet?>?0)?{

if?(inputLen?-?offSet?>?MAX_ENCRYPT_BLOCK)?{

cache?=?cipher.doFinal(data,?offSet,?MAX_ENCRYPT_BLOCK);

}?else?{

cache?=?cipher.doFinal(data,?offSet,?inputLen?-?offSet);

}

out.write(cache,?0,?cache.length);

i++;

offSet?=?i?*?MAX_ENCRYPT_BLOCK;

}

byte[]?encryptedData?=?out.toByteArray();

out.close();

return?encryptedData;

}

/**

*?

*?獲取私鑰

*?

*

*?@param?keyMap?密鑰對

*?@return

*?@throws?Exception

*/

public?static?String?getPrivateKey(Map?keyMap)

throws?Exception?{

Key?key?=?(Key)?keyMap.get(PRIVATE_KEY);

return?Base64Utils.encode(key.getEncoded());

}

/**

*?

*?獲取公鑰

*?

*

*?@param?keyMap?密鑰對

*?@return

*?@throws?Exception

*/

public?static?String?getPublicKey(Map?keyMap)

throws?Exception?{

Key?key?=?(Key)?keyMap.get(PUBLIC_KEY);

return?Base64Utils.encode(key.getEncoded());

}

}

Base64Utils.javaimport?java.io.ByteArrayInputStream;

import?java.io.ByteArrayOutputStream;

import?java.io.File;

import?java.io.FileInputStream;

import?java.io.FileOutputStream;

import?java.io.InputStream;

import?java.io.OutputStream;

import?it.sauronsoftware.base64.Base64;

/**

*?

*?BASE64編碼解碼工具包

*?

*?

*?依賴javabase64-1.3.1.jar

*?

*

*?@author?IceWee

*?@date?2012-5-19

*?@version?1.0

*/

public?class?Base64Utils?{

/**

*?文件讀取緩沖區大小

*/

private?static?final?int?CACHE_SIZE?=?1024;

/**

*?

*?BASE64字符串解碼為二進制數據

*?

*

*?@param?base64

*?@return

*?@throws?Exception

*/

public?static?byte[]?decode(String?base64)?throws?Exception?{

return?Base64.decode(base64.getBytes());

}

/**

*?

*?二進制數據編碼為BASE64字符串

*?

*

*?@param?bytes

*?@return

*?@throws?Exception

*/

public?static?String?encode(byte[]?bytes)?throws?Exception?{

return?new?String(Base64.encode(bytes));

}

/**

*?

*?將文件編碼為BASE64字符串

*?

*?

*?大文件慎用，可能會導致內存溢出

*?

*

*?@param?filePath?文件絕對路徑

*?@return

*?@throws?Exception

*/

public?static?String?encodeFile(String?filePath)?throws?Exception?{

byte[]?bytes?=?fileToByte(filePath);

return?encode(bytes);

}

/**

*?

*?BASE64字符串轉回文件

*?

*

*?@param?filePath?文件絕對路徑

*?@param?base64?編碼字符串

*?@throws?Exception

*/

public?static?void?decodeToFile(String?filePath,?String?base64)?throws?Exception?{

byte[]?bytes?=?decode(base64);

byteArrayToFile(bytes,?filePath);

}

/**

*?

*?文件轉換為二進制數組

*?

*

*?@param?filePath?文件路徑

*?@return

*?@throws?Exception

*/

public?static?byte[]?fileToByte(String?filePath)?throws?Exception?{

byte[]?data?=?new?byte[0];

File?file?=?new?File(filePath);

if?(file.exists())?{

FileInputStream?in?=?new?FileInputStream(file);

ByteArrayOutputStream?out?=?new?ByteArrayOutputStream(2048);

byte[]?cache?=?new?byte[CACHE_SIZE];

int?nRead?=?0;

while?((nRead?=?in.read(cache))?!=?-1)?{

out.write(cache,?0,?nRead);

out.flush();

}

out.close();

in.close();

data?=?out.toByteArray();

}

return?data;

}

/**

*?

*?二進制數據寫文件

*?

*

*?@param?bytes?二進制數據

*?@param?filePath?文件生成目錄

*/

public?static?void?byteArrayToFile(byte[]?bytes,?String?filePath)?throws?Exception?{

InputStream?in?=?new?ByteArrayInputStream(bytes);

File?destFile?=?new?File(filePath);

if?(!destFile.getParentFile().exists())?{

destFile.getParentFile().mkdirs();

}

destFile.createNewFile();

OutputStream?out?=?new?FileOutputStream(destFile);

byte[]?cache?=?new?byte[CACHE_SIZE];

int?nRead?=?0;

while?((nRead?=?in.read(cache))?!=?-1)?{

out.write(cache,?0,?nRead);

out.flush();

}

out.close();

in.close();

}

}

RSATester.javaimport?java.util.Map;

public?class?RSATester?{

static?String?publicKey;

static?String?privateKey;

static?{

try?{

Map?keyMap?=?RSAUtils.genKeyPair();

publicKey?=?RSAUtils.getPublicKey(keyMap);

privateKey?=?RSAUtils.getPrivateKey(keyMap);

System.err.println("公鑰:?\n\r"?+?publicKey);

System.err.println("私鑰：?\n\r"?+?privateKey);

}?catch?(Exception?e)?{

e.printStackTrace();

}

}

public?static?void?main(String[]?args)?throws?Exception?{

test();

testSign();

}

static?void?test()?throws?Exception?{

System.err.println("公鑰加密——私鑰解密");

String?source?=?"這是一行沒有任何意義的文字，你看完了等于沒看，不是嗎？";

System.out.println("\r加密前文字：\r\n"?+?source);

byte[]?data?=?source.getBytes();

byte[]?encodedData?=?RSAUtils.encryptByPublicKey(data,?publicKey);

System.out.println("加密后文字：\r\n"?+?new?String(encodedData));

byte[]?decodedData?=?RSAUtils.decryptByPrivateKey(encodedData,?privateKey);

String?target?=?new?String(decodedData);

System.out.println("解密后文字:?\r\n"?+?target);

}

static?void?testSign()?throws?Exception?{

System.err.println("私鑰加密——公鑰解密");

String?source?=?"這是一行測試RSA數字簽名的無意義文字";

System.out.println("原文字：\r\n"?+?source);

byte[]?data?=?source.getBytes();

byte[]?encodedData?=?RSAUtils.encryptByPrivateKey(data,?privateKey);

System.out.println("加密后：\r\n"?+?new?String(encodedData));

byte[]?decodedData?=?RSAUtils.decryptByPublicKey(encodedData,?publicKey);

String?target?=?new?String(decodedData);

System.out.println("解密后:?\r\n"?+?target);

System.err.println("私鑰簽名——公鑰驗證簽名");

String?sign?=?RSAUtils.sign(encodedData,?privateKey);

System.err.println("簽名:\r"?+?sign);

boolean?status?=?RSAUtils.verify(encodedData,?publicKey,?sign);

System.err.println("驗證結果:\r"?+?status);

}

}

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