这期内容当中小编将会给大家带来有关如何在Java中使用RSA加密对密码进行加密解密，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。
具体如下：
public static void main(String[] args) throws Exception { // TODO Auto-generated method stub HashMap<String, Object> map = RSAUtils.getKeys(); //生成公钥和私钥 RSAPublicKey publicKey = (RSAPublicKey) map.get("public"); RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private"); //模 String modulus = publicKey.getModulus().toString(); //公钥指数 String public_exponent = publicKey.getPublicExponent().toString(); //私钥指数 String private_exponent = privateKey.getPrivateExponent().toString(); //明文 String ming = "123456789"; //使用模和指数生成公钥和私钥 RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent); RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent); //加密后的密文 String mi = RSAUtils.encryptByPublicKey(ming, pubKey); System.err.println(mi); //解密后的明文 ming = RSAUtils.decryptByPrivateKey(mi, priKey); System.err.println(ming);}RSAUtils.Java
package yyy.test.rsa;import java.math.BigInteger;import java.security.KeyFactory;import java.security.KeyPair;import java.security.KeyPairGenerator;import java.security.NoSuchAlgorithmException;import java.security.interfaces.RSAPrivateKey;import java.security.interfaces.RSAPublicKey;import java.security.spec.RSAPrivateKeySpec;import java.security.spec.RSAPublicKeySpec;import java.util.HashMap;import javax.crypto.Cipher;public class RSAUtils { public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException{ HashMap<String, Object> map = new HashMap<String, Object>(); KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA"); keyPairGen.initialize(1024); KeyPair keyPair = keyPairGen.generateKeyPair(); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); map.put("public", publicKey); map.put("private", privateKey); return map; } public static RSAPublicKey getPublicKey(String modulus, String exponent) { try { BigInteger b1 = new BigInteger(modulus); BigInteger b2 = new BigInteger(exponent); KeyFactory keyFactory = KeyFactory.getInstance("RSA"); RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2); return (RSAPublicKey) keyFactory.generatePublic(keySpec); } catch (Exception e) { e.printStackTrace(); return null; } } public static RSAPrivateKey getPrivateKey(String modulus, String exponent) { try { BigInteger b1 = new BigInteger(modulus); BigInteger b2 = new BigInteger(exponent); KeyFactory keyFactory = KeyFactory.getInstance("RSA"); RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2); return (RSAPrivateKey) keyFactory.generatePrivate(keySpec); } catch (Exception e) { e.printStackTrace(); return null; } } public static String encryptByPublicKey(String data, RSAPublicKey publicKey) throws Exception { Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); // 模长 int key_len = publicKey.getModulus().bitLength() / 8; // 加密数据长度 <= 模长-11 String[] datas = splitString(data, key_len - 11); String mi = ""; //如果明文长度大于模长-11则要分组加密 for (String s : datas) { mi += bcd2Str(cipher.doFinal(s.getBytes())); } return mi; } public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey) throws Exception { Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.DECRYPT_MODE, privateKey); //模长 int key_len = privateKey.getModulus().bitLength() / 8; byte[] bytes = data.getBytes(); byte[] bcd = ASCII_To_BCD(bytes, bytes.length); System.err.println(bcd.length); //如果密文长度大于模长则要分组解密 String ming = ""; byte[][] arrays = splitArray(bcd, key_len); for(byte[] arr : arrays){ ming += new String(cipher.doFinal(arr)); } return ming; } public static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) { byte[] bcd = new byte[asc_len / 2]; int j = 0; for (int i = 0; i < (asc_len + 1) / 2; i++) { bcd[i] = asc_to_bcd(ascii[j++]); bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4)); } return bcd; } public static byte asc_to_bcd(byte asc) { byte bcd; if ((asc >= '0') && (asc <= '9')) bcd = (byte) (asc - '0'); else if ((asc >= 'A') && (asc <= 'F')) bcd = (byte) (asc - 'A' + 10); else if ((asc >= 'a') && (asc <= 'f')) bcd = (byte) (asc - 'a' + 10); else bcd = (byte) (asc - 48); return bcd; } public static String bcd2Str(byte[] bytes) { char temp[] = new char[bytes.length * 2], val; for (int i = 0; i < bytes.length; i++) { val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f); temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0'); val = (char) (bytes[i] & 0x0f); temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0'); } return new String(temp); } public static String[] splitString(String string, int len) { int x = string.length() / len; int y = string.length() % len; int z = 0; if (y != 0) { z = 1; } String[] strings = new String[x + z]; String str = ""; for (int i=0; i<x+z; i++) { if (i==x+z-1 && y!=0) { str = string.substring(i*len, i*len+y); }else{ str = string.substring(i*len, i*len+len); } strings[i] = str; } return strings; } public static byte[][] splitArray(byte[] data,int len){ int x = data.length / len; int y = data.length % len; int z = 0; if(y!=0){ z = 1; } byte[][] arrays = new byte[x+z][]; byte[] arr; for(int i=0; i<x+z; i++){ arr = new byte[len]; if(i==x+z-1 && y!=0){ System.arraycopy(data, i*len, arr, 0, y); }else{ System.arraycopy(data, i*len, arr, 0, len); } arrays[i] = arr; } return arrays; }}java
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");android
Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");参考:
http://stackoverflow.com/questions/6069369/rsa-encryption-difference-between-java-and-android
http://stackoverflow.com/questions/2956647/rsa-encrypt-with-base64-encoded-public-key-in-android
补充：关于RSA算法密钥长度/密文长度/明文长度
1.密钥长度
rsa算法初始化的时候一般要填入密钥长度,在96-1024bits间
(1)为啥下限是96bits(12bytes)?因为加密1byte的明文,需要至少1+11=12bytes的密钥(不懂?看下面的明文长度),低于下限96bits时,一个byte都加密不了,当然没意义啦
(2)为啥上限是1024(128bytes)?这是算法本身决定的...当然如果某天网上出现了支持2048bits长的密钥的rsa算法时,你当我废话吧
2.明文长度
明文长度(bytes) <= 密钥长度(bytes)-11.这样的话,对于上限密钥长度1024bits能加密的明文上限就是117bytes了.
这个规定很狗血,所以就出现了分片加密,网上很流行这个版本.很简单,如果明文长度大于那个最大明文长度了,我就分片吧,保证每片都别超过那个值就是了.
片数=(明文长度(bytes)/(密钥长度(bytes)-11))的整数部分+1,就是不满一片的按一片算
3.密文长度
对,就是这个充满了谣言,都说密文长度为密钥长度的一半,经俺验证,密文长度等于密钥长度.当然这是不分片情况下的.
分片后,密文长度=密钥长度*片数
例如96bits的密钥,明文4bytes
每片明文长度=96/8-11=1byte,片数=4,密文长度=96/8*4=48bytes
又例如128bits的密钥,明文8bytes
每片明文长度=128/8-11=5bytes,片数=8/5取整+1=2,密文长度=128/8*2=32
注意,对于指定长度的明文,其密文长度与密钥长度非正比关系.如4bytes的明文,在最短密钥96bites是,密文长度48bytes,128bits米密钥时,密文长度为16bytes,1024bits密钥时,密文长度128bytes.
因 为分片越多,密文长度显然会变大,所以有人说,那就一直用1024bits的密钥吧...拜托,现在的机器算1024bits的密钥还是要点时间滴,别以 为你的cpu很牛逼...那么选个什么值比较合适呢?个人认为是600bits,因为我们对于一个字符串的加密,一般不是直接加密,而是将字符串hash 后,对hash值加密.现在的hash值一般都是4bytes,很少有8bytes,几十年内应该也不会超过64bytes.那就用64bytes算吧, 密钥长度就是(64+11)*8=600bits了.
用开源rsa算法的时候,还要注意,那个年代的人把long当4bytes用,如今 放在64位的机器上,就会死循环啊多悲催....因为有个循环里让一个4bytes做递减....64位机上long是8bytes,这个循环进去后个把 小时都出不来....所以要注意下哦....同理对于所有年代久远的开源库都得注意下...
上述就是小编为大家分享的如何在Java中使用RSA加密对密码进行加密解密了，如果刚好有类似的疑惑，不妨参照上述分析进行理解。如果想知道更多相关知识，欢迎关注编程网行业资讯频道。
