android开发中Rsa加密的使用
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一、RSA加密算法的介绍
RSA算法是一种非对称密码算法,所谓非对称,就是指该算法需要一对密钥,使用其中一个加密,则需要用另一个才能解密。
RSA是可逆的,一个字符串可以经rsa加密后,经加密后的字符串传到对端如服务器上,再进行解密即可。前提是服务器知道解密的私钥,当然这个私钥最好不要再网络传输。
RSA的算法涉及三个参数,n、e1、e2。 其中,n是两个大质数p、q的积,n的二进制表示时所占用的位数,就是所谓的密钥长度。 e1和e2是一对相关的值,e1可以任意取,但要求e1与(p-1)*(q-1)互质;再选择e2,要求
(e2*e1)mod((p-1)*(q-1))=1。
(n及e1),(n及e2)就是密钥对。
RSA加解密的算法完全相同,设A为明文,B为密文,则:A=B^e1 mod n;B=A^e2 mod n;
e1和e2可以互换使用,即:
A=B^e2 mod n;B=A^e1 mod n;
补充:
对明文进行加密,有两种情况需要这样作:
1、您向朋友传送加密数据,您希望只有您的朋友可以解密,这样的话,您需要首先获取您朋友的密钥对中公开的那一个密钥,e及n。然后用这个密钥进行加密,这样密文只有您的朋友可以解密,因为对应的私钥只有您朋友拥有。
2、您向朋友传送一段数据附加您的数字签名,您需要对您的数据进行MD5之类的运算以取得数据的”指纹”,再对”指纹”进行加密,加密将使用您自己的密钥对中的不公开的私钥。您的朋友收到数据后,用同样的运算获得数据指纹,再用您的公钥对加密指纹进行解密,比较解密结果与他自己计算出来的指纹是否一致,即可确定数据是否的确是您发送的、以及在传输过程中是否被篡改。
密钥的获得,通常由某个机构颁发(如CA中心),当然也可以由您自己创建密钥,但这样作,您的密钥并不具有权威性。
计算方面,按公式计算就行了,如果您的加密强度为1024位,则结果会在有效数据前面补0以补齐不足的位数。补入的0并不影响解密运算。
下面是java实现RSAUtil.java类:
/**
* Created by jie.fan on 2016/2/29.
*/
public final class RsaUtils {
private static String RSA = "RSA";/** * 随机生成RSA密钥对(默认密钥长度为1024) * * @return */public static KeyPair generateRSAKeyPair(){ return generateRSAKeyPair(1024);}/** * 随机生成RSA密钥对 * * @param keyLength * 密钥长度,范围:512~2048<br> * 一般1024 * @return */public static KeyPair generateRSAKeyPair(int keyLength){ try { KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA); kpg.initialize(keyLength); return kpg.genKeyPair(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); return null; }}/** * 用公钥加密 <br> * 每次加密的字节数,不能超过密钥的长度值减去11 * * @param data * 需加密数据的byte数据 * @return 加密后的byte型数据 */public static byte[] encryptData(byte[] data, PublicKey publicKey){ try { Cipher cipher = Cipher.getInstance(RSA); // 编码前设定编码方式及密钥 cipher.init(Cipher.ENCRYPT_MODE, publicKey); // 传入编码数据并返回编码结果 return cipher.doFinal(data); } catch (Exception e) { e.printStackTrace(); return null; }}/** * 用私钥解密 * * @param encryptedData * 经过encryptedData()加密返回的byte数据 * @param privateKey * 私钥 * @return */public static byte[] decryptData(byte[] encryptedData, PrivateKey privateKey){ try { Cipher cipher = Cipher.getInstance(RSA); cipher.init(Cipher.DECRYPT_MODE, privateKey); return cipher.doFinal(encryptedData); } catch (Exception e) { return null; }}/** * 通过公钥byte[](publicKey.getEncoded())将公钥还原,适用于RSA算法 * * @param keyBytes * @return * @throws NoSuchAlgorithmException * @throws InvalidKeySpecException */public static PublicKey getPublicKey(byte[] keyBytes) throws NoSuchAlgorithmException, InvalidKeySpecException{ X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes); KeyFactory keyFactory = KeyFactory.getInstance(RSA); PublicKey publicKey = keyFactory.generatePublic(keySpec); return publicKey;}/** * 通过私钥byte[]将公钥还原,适用于RSA算法 * * @param keyBytes * @return * @throws NoSuchAlgorithmException * @throws InvalidKeySpecException */public static PrivateKey getPrivateKey(byte[] keyBytes) throws NoSuchAlgorithmException, InvalidKeySpecException{ PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes); KeyFactory keyFactory = KeyFactory.getInstance(RSA); PrivateKey privateKey = keyFactory.generatePrivate(keySpec); return privateKey;}/** * 使用N、e值还原公钥 * * @param modulus * @param publicExponent * @return * @throws NoSuchAlgorithmException * @throws InvalidKeySpecException */public static PublicKey getPublicKey(String modulus, String publicExponent) throws NoSuchAlgorithmException, InvalidKeySpecException{ BigInteger bigIntModulus = new BigInteger(modulus); BigInteger bigIntPrivateExponent = new BigInteger(publicExponent); RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent); KeyFactory keyFactory = KeyFactory.getInstance(RSA); PublicKey publicKey = keyFactory.generatePublic(keySpec); return publicKey;}/** * 使用N、d值还原私钥 * * @param modulus * @param privateExponent * @return * @throws NoSuchAlgorithmException * @throws InvalidKeySpecException */public static PrivateKey getPrivateKey(String modulus, String privateExponent) throws NoSuchAlgorithmException, InvalidKeySpecException{ BigInteger bigIntModulus = new BigInteger(modulus); BigInteger bigIntPrivateExponent = new BigInteger(privateExponent); RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntPrivateExponent); KeyFactory keyFactory = KeyFactory.getInstance(RSA); PrivateKey privateKey = keyFactory.generatePrivate(keySpec); return privateKey;}/** * 从字符串中加载公钥 * * @param publicKeyStr * 公钥数据字符串 * @throws Exception * 加载公钥时产生的异常 */public static PublicKey loadPublicKey(String publicKeyStr) throws Exception{ try { byte[] buffer = Base64Utils.decode(publicKeyStr.getBytes()); KeyFactory keyFactory = KeyFactory.getInstance(RSA); X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer); return (RSAPublicKey) keyFactory.generatePublic(keySpec); } catch (NoSuchAlgorithmException e) { throw new Exception("无此算法"); } catch (InvalidKeySpecException e) { throw new Exception("公钥非法"); } catch (NullPointerException e) { throw new Exception("公钥数据为空"); }}/** * 从字符串中加载私钥<br> * 加载时使用的是PKCS8EncodedKeySpec(PKCS#8编码的Key指令)。 * * @param privateKeyStr * @return * @throws Exception */public static PrivateKey loadPrivateKey(String privateKeyStr) throws Exception{ try { byte[] buffer = Base64Utils.decode(privateKeyStr.getBytes()); // X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer); PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer); KeyFactory keyFactory = KeyFactory.getInstance(RSA); return (RSAPrivateKey) keyFactory.generatePrivate(keySpec); } catch (NoSuchAlgorithmException e) { throw new Exception("无此算法"); } catch (InvalidKeySpecException e) { throw new Exception("私钥非法"); } catch (NullPointerException e) { throw new Exception("私钥数据为空"); }}/** * 从文件中输入流中加载公钥 * * @param in * 公钥输入流 * @throws Exception * 加载公钥时产生的异常 */public static PublicKey loadPublicKey(InputStream in) throws Exception{ try { return loadPublicKey(readKey(in)); } catch (IOException e) { throw new Exception("公钥数据流读取错误"); } catch (NullPointerException e) { throw new Exception("公钥输入流为空"); }}/** * 从文件中加载私钥 * * @return 是否成功 * @throws Exception */public static PrivateKey loadPrivateKey(InputStream in) throws Exception{ try { return loadPrivateKey(readKey(in)); } catch (IOException e) { throw new Exception("私钥数据读取错误"); } catch (NullPointerException e) { throw new Exception("私钥输入流为空"); }}/** * 读取密钥信息 * * @param in * @return * @throws IOException */private static String readKey(InputStream in) throws IOException{ BufferedReader br = new BufferedReader(new InputStreamReader(in)); String readLine = null; StringBuilder sb = new StringBuilder(); while ((readLine = br.readLine()) != null) { if (readLine.charAt(0) == '-') { continue; } else { sb.append(readLine); sb.append('\r'); } } return sb.toString();}/** * 打印公钥信息 * * @param publicKey */public static void printPublicKeyInfo(PublicKey publicKey){ RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey; System.out.println("----------RSAPublicKey----------"); System.out.println("Modulus.length=" + rsaPublicKey.getModulus().bitLength()); System.out.println("Modulus=" + rsaPublicKey.getModulus().toString()); System.out.println("PublicExponent.length=" + rsaPublicKey.getPublicExponent().bitLength()); System.out.println("PublicExponent=" + rsaPublicKey.getPublicExponent().toString());}public static void printPrivateKeyInfo(PrivateKey privateKey){ RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey; System.out.println("----------RSAPrivateKey ----------"); System.out.println("Modulus.length=" + rsaPrivateKey.getModulus().bitLength()); System.out.println("Modulus=" + rsaPrivateKey.getModulus().toString()); System.out.println("PrivateExponent.length=" + rsaPrivateKey.getPrivateExponent().bitLength()); System.out.println("PrivatecExponent=" + rsaPrivateKey.getPrivateExponent().toString());}
}
下面是java实现Base64Utils.java类:
/**
* Created by jie.fan on 2016/3/1.
*/
public class Base64Utils {
private static char[] base64EncodeChars = new char[] {‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, ‘H’, ‘I’, ‘J’, ‘K’, ‘L’, ‘M’, ‘N’, ‘O’, ‘P’, ‘Q’, ‘R’, ‘S’, ‘T’, ‘U’, ‘V’, ‘W’, ‘X’, ‘Y’, ‘Z’, ‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’, ‘0’, ‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ‘+’, ‘/’};
private static byte[] base64DecodeChars = new byte[] {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1};
/** * 加密 * * @param data * @return */public static String encode(byte[] data) { StringBuffer sb = new StringBuffer(); int len = data.length; int i = 0; int b1, b2, b3; while (i < len) { b1 = data[i++] & 0xff; if (i == len) { sb.append(base64EncodeChars[b1 >>> 2]); sb.append(base64EncodeChars[(b1 & 0x3) << 4]); sb.append("=="); break; } b2 = data[i++] & 0xff; if (i == len) { sb.append(base64EncodeChars[b1 >>> 2]); sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]); sb.append(base64EncodeChars[(b2 & 0x0f) << 2]); sb.append("="); break; } b3 = data[i++] & 0xff; sb.append(base64EncodeChars[b1 >>> 2]); sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]); sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]); sb.append(base64EncodeChars[b3 & 0x3f]); } return sb.toString();}/** * 解密 * * @param str * @return */public static byte[] decode(String str) { try { return decodePrivate(str); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } return new byte[] {};}private static byte[] decodePrivate(String str) throws UnsupportedEncodingException { StringBuffer sb = new StringBuffer(); byte[] data = null; data = str.getBytes("US-ASCII"); int len = data.length; int i = 0; int b1, b2, b3, b4; while (i < len) { do { b1 = base64DecodeChars[data[i++]]; } while (i < len && b1 == -1); if (b1 == -1) break; do { b2 = base64DecodeChars[data[i++]]; } while (i < len && b2 == -1); if (b2 == -1) break; sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4))); do { b3 = data[i++]; if (b3 == 61) return sb.toString().getBytes("iso8859-1"); b3 = base64DecodeChars[b3]; } while (i < len && b3 == -1); if (b3 == -1) break; sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2))); do { b4 = data[i++]; if (b4 == 61) return sb.toString().getBytes("iso8859-1"); b4 = base64DecodeChars[b4]; } while (i < len && b4 == -1); if (b4 == -1) break; sb.append((char) (((b3 & 0x03) << 6) | b4)); } return sb.toString().getBytes("iso8859-1");}
}
二、RSA加密算法的使用
对以下字符串加密
String preEncryStr = “fanjie”;
//1.密匙的获取
1>生成密匙对
KeyPair keyPair = RsaUtils.generateRSAKeyPair();
PublicKey publicKey = keyPair.getPublic();
PrivateKey privateKey = keyPair.getPrivate();
2>从字符串获得公、私匙
/* 密钥内容 base64 code */
private static String PUCLIC_KEY = “MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCfRTdcPIH10gT9f31rQuIInLwe”
+ “\r” + “7fl2dtEJ93gTmjE9c2H+kLVENWgECiJVQ5sonQNfwToMKdO0b3Olf4pgBKeLThra” + “\r”
+ “z/L3nYJYlbqjHC3jTjUnZc0luumpXGsox62+PuSGBlfb8zJO6hix4GV/vhyQVCpG” + “\r”
+ “9aYqgE7zyTRZYX9byQIDAQAB” + “\r”;
private static String PRIVATE_KEY = “MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAJ9FN1w8gfXSBP1/”
+ “\r” + “fWtC4gicvB7t+XZ20Qn3eBOaMT1zYf6QtUQ1aAQKIlVDmyidA1/BOgwp07Rvc6V/” + “\r”
+ “imAEp4tOGtrP8vedgliVuqMcLeNONSdlzSW66alcayjHrb4+5IYGV9vzMk7qGLHg” + “\r”
+ “ZX++HJBUKkb1piqATvPJNFlhf1vJAgMBAAECgYA736xhG0oL3EkN9yhx8zG/5RP/” + “\r”
+ “WJzoQOByq7pTPCr4m/Ch30qVerJAmoKvpPumN+h1zdEBk5PHiAJkm96sG/PTndEf” + “\r”
+ “kZrAJ2hwSBqptcABYk6ED70gRTQ1S53tyQXIOSjRBcugY/21qeswS3nMyq3xDEPK” + “\r”
+ “XpdyKPeaTyuK86AEkQJBAM1M7p1lfzEKjNw17SDMLnca/8pBcA0EEcyvtaQpRvaL” + “\r”
+ “n61eQQnnPdpvHamkRBcOvgCAkfwa1uboru0QdXii/gUCQQDGmkP+KJPX9JVCrbRt” + “\r”
+ “7wKyIemyNM+J6y1ZBZ2bVCf9jacCQaSkIWnIR1S9UM+1CFE30So2CA0CfCDmQy+y” + “\r”
+ “7A31AkB8cGFB7j+GTkrLP7SX6KtRboAU7E0q1oijdO24r3xf/Imw4Cy0AAIx4KAu” + “\r”
+ “L29GOp1YWJYkJXCVTfyZnRxXHxSxAkEAvO0zkSv4uI8rDmtAIPQllF8+eRBT/deD” + “\r”
+ “JBR7ga/k+wctwK/Bd4Fxp9xzeETP0l8/I+IOTagK+Dos8d8oGQUFoQJBAI4Nwpfo” + “\r”
+ “MFaLJXGY9ok45wXrcqkJgM+SN6i8hQeujXESVHYatAIL/1DgLi+u46EFD69fw0w+” + “\r” + “c7o0HLlMsYPAzJw=”
+ “\r”;
PublicKey publicKey = RSAUtils.loadPublicKey(PUCLIC_KEY);
PrivateKey privateKey = RSAUtils.loadPrivateKey(PRIVATE_KEY);
3>从文件中获取.pem密匙证书文件
InputStream inPublic = getResources().getAssets().open(“rsa_public_key.pem”);
publicKey = RSAUtils.loadPublicKey(inPublic);
私匙,同理
//2.用公匙加密
byte[] enArr = RsaUtils.encryptData(preEncryStr.getBytes(), publicKey);
//使用base64编码,防止出现乱码
byte[] enBase64Arr= Base64Utils.encode(enArr);
//不要用toString(),会出现乱码
String preDecryStr = new String(enBase64Arr);
//记得解码哦
byte[] deBase64Arr = Base64Utils.decode(preDecryStr);
//3.用私匙解密
byte[] decryptByte = RsaUtils.decryptData(deBase64Arr, privateKey);
String decryptStr = new String(decryptByte);
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