Android使用RSA加密和解密的示例代码
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2023-12-10 13:31:10
一、公钥加密和私钥解密
/**rsa算法*/
public static final string rsa = "rsa";
/**加密方式，an...
一、公钥加密和私钥解密
/**rsa算法*/
public static final string rsa = "rsa";
/**加密方式，android的*/
// public static final string transformation = "rsa/none/nopadding";
/**加密方式，标准jdk的*/
public static final string transformation = "rsa/none/pkcs1padding";
/** 使用公钥加密 */
public static byte[] encryptbypublickey(byte[] data, byte[] publickey) throws exception {
// 得到公钥对象
x509encodedkeyspec keyspec = new x509encodedkeyspec(publickey);
keyfactory keyfactory = keyfactory.getinstance("rsa");
publickey pubkey = keyfactory.generatepublic(keyspec);
// 加密数据
cipher cp = cipher.getinstance(transformation);
cp.init(cipher.encrypt_mode, pubkey);
return cp.dofinal(data);
}
/** 使用私钥解密 */
public static byte[] decryptbyprivatekey(byte[] encrypted, byte[] privatekey) throws exception {
// 得到私钥对象
pkcs8encodedkeyspec keyspec = new pkcs8encodedkeyspec(privatekey);
keyfactory kf = keyfactory.getinstance(rsa);
privatekey keyprivate = kf.generateprivate(keyspec);
// 解密数据
cipher cp = cipher.getinstance(transformation);
cp.init(cipher.decrypt_mode, keyprivate);
byte[] arr = cp.dofinal(encrypted);
return arr;
}
1.data是要加密的数据，如果是字符串则getbytes。publickey是公钥，privatekey是私钥。自定义密钥对测试
string data = "hello world";
try {
int keylength = 1024;
//生成密钥对
keypair keypair = rsautils.generatersakeypair(keylength);
//获取公钥
byte[] publickey = rsautils.getpublickey(keypair);
//获取私钥
byte[] privatekey = rsautils.getprivatekey(keypair);
//用公钥加密
byte[] encrypt = rsautils.encryptbypublickey(data.getbytes(), publickey);
log.d("tag", "加密后的数据：" + stringutils.bytearraytostring(encrypt));
//用私钥解密
byte[] decrypt = rsautils.decryptbyprivatekey(encrypt, privatekey);
log.d("tag", "解密后的数据：" + new string(decrypt, "utf-8"));
} catch (exception e) {
e.printstacktrace();
}
2.从文件中读取公钥
string data = "hello world";
//读取公钥文件
string publickeystring = ioutils.readassetsfile(this, "rsa_public_key.pem");
//base64解码
byte[] publickey = base64utils.decodetobytes(publickeystring);
try {
//加密
byte[] encrypt = rsautils.encryptbypublickey(data.getbytes(), publickey);
log.d("tag", "加密后的数据：" + stringutils.bytearraytostring(encrypt));
// //读取私钥文件
// string privatekeystring = ioutils.readassetsfile(this, "rsa_private_key.pem");
// //base64解码
// byte[] privatekey = base64utils.decodetobytes(privatekeystring);
// //解密
// byte[] decrypt = rsautils.decryptbyprivatekey(encrypt, privatekey);
// log.d("tag", "解密后的数据：" + new string(decrypt, "utf-8"));
} catch (exception e) {
e.printstacktrace();
}
二、公钥分段加密和私钥分段解密
当加密的数据过长时，会出现javax.crypto.illegalblocksizeexception: data must not be longer than 117 bytes的异常。rsa算法规定一次加密的数据不能超过生成密钥对时的keylength/8-11，keylength一般是1024个字节，则加密的数据不能超过117个字节
/**秘钥默认长度*/
public static final int default_key_size = 1024;
/**加密的数据最大的字节数，即117个字节*/
public static final int default_buffersize = (default_key_size / 8) - 11;
/**当加密的数据超过default_buffersize，则使用分段加密*/
public static final byte[] default_split = "#part#".getbytes();
/** 使用公钥分段加密 */
public static byte[] encryptbypublickeyforspilt(byte[] data, byte[] publickey) throws exception{
int datalen = data.length;
if (datalen <= default_buffersize) {
return encryptbypublickey(data, publickey);
}
list<byte> allbytes = new arraylist<byte>(2048);
int bufindex = 0;
int subdataloop = 0;
byte[] buf = new byte[default_buffersize];
for (int i = 0; i < datalen; i++) {
buf[bufindex] = data[i];
if (++bufindex == default_buffersize || i == datalen - 1) {
subdataloop++;
if (subdataloop != 1) {
for (byte b : default_split) {
allbytes.add(b);
}
}
byte[] encryptbytes = encryptbypublickey(buf, publickey);
for (byte b : encryptbytes) {
allbytes.add(b);
}
bufindex = 0;
if (i == datalen - 1) {
buf = null;
} else {
buf = new byte[math
.min(default_buffersize, datalen - i - 1)];
}
}
}
byte[] bytes = new byte[allbytes.size()];
int i = 0;
for (byte b : allbytes) {
bytes[i++] = b.bytevalue();
}
return bytes;
}
/** 使用私钥分段解密 */
public static byte[] decryptbyprivatekeyforspilt(byte[] encrypted, byte[] privatekey) throws exception {
int splitlen = default_split.length;
if (splitlen <= 0) {
return decryptbyprivatekey(encrypted, privatekey);
}
int datalen = encrypted.length;
list<byte> allbytes = new arraylist<byte>(1024);
int lateststartindex = 0;
for (int i = 0; i < datalen; i++) {
byte bt = encrypted[i];
boolean ismatchsplit = false;
if (i == datalen - 1) {
// 到data的最后了
byte[] part = new byte[datalen - lateststartindex];
system.arraycopy(encrypted, lateststartindex, part, 0, part.length);
byte[] decryptpart = decryptbyprivatekey(part, privatekey);
for (byte b : decryptpart) {
allbytes.add(b);
}
lateststartindex = i + splitlen;
i = lateststartindex - 1;
} else if (bt == default_split[0]) {
// 这个是以split[0]开头
if (splitlen > 1) {
if (i + splitlen < datalen) {
// 没有超出data的范围
for (int j = 1; j < splitlen; j++) {
if (default_split[j] != encrypted[i + j]) {
break;
}
if (j == splitlen - 1) {
// 验证到split的最后一位，都没有break，则表明已经确认是split段
ismatchsplit = true;
}
}
}
} else {
// split只有一位，则已经匹配了
ismatchsplit = true;
}
}
if (ismatchsplit) {
byte[] part = new byte[i - lateststartindex];
system.arraycopy(encrypted, lateststartindex, part, 0, part.length);
byte[] decryptpart = decryptbyprivatekey(part, privatekey);
for (byte b : decryptpart) {
allbytes.add(b);
}
lateststartindex = i + splitlen;
i = lateststartindex - 1;
}
}
byte[] bytes = new byte[allbytes.size()];
int i = 0;
for (byte b : allbytes) {
bytes[i++] = b.bytevalue();
}
return bytes;
}
测试分段加密和解密
string data = "hello world hello world hello world hello world hello world hello world hello world hello world " +
"hello world hello world hello world hello world hello world hello world hello world hello world hello world " +
"hello world hello world hello world hello world hello world hello world hello world hello world hello world ";
log.d("tag", "要加密的数据：" + data + ", 要加密的数据长度：" + data.length());
try {
//分段加密
byte[] encrypt = rsautils.encryptbypublickeyforspilt(data.getbytes(), publickey);
log.d("tag", "加密后的数据：" + stringutils.bytearraytostring(encrypt));
//分段解密
byte[] decrypt = rsautils.decryptbyprivatekeyforspilt(encrypt, privatekey);
log.d("tag", "解密后的数据：" + new string(decrypt, "utf-8"));
} catch (exception e) {
e.printstacktrace();
}
三、生成密钥对
/** 生成密钥对，即公钥和私钥。key长度是512-2048，一般为1024 */
public static keypair generatersakeypair(int keylength) throws nosuchalgorithmexception {
keypairgenerator kpg = keypairgenerator.getinstance(rsa);
kpg.initialize(keylength);
return kpg.genkeypair();
}
/** 获取公钥，打印为48-12613448136942-12272-122-913111503-126115048-12...等等一长串用-拼接的数字 */
public static byte[] getpublickey(keypair keypair) {
rsapublickey rsapublickey = (rsapublickey) keypair.getpublic();
return rsapublickey.getencoded();
}
/** 获取私钥，同上 */
public static byte[] getprivatekey(keypair keypair) {
rsaprivatekey rsaprivatekey = (rsaprivatekey) keypair.getprivate();
return rsaprivatekey.getencoded();
}
生成公钥和私钥后，用base64编码
int keylength = 1024;
try {
//生成密钥对
keypair keypair = rsautils.generatersakeypair(keylength);
//获取公钥
byte[] publickey = rsautils.getpublickey(keypair);
log.d("tag", "公钥：" + stringutils.bytearraytostring(publickey));
//公钥用base64编码
string encodepublic = base64utils.encodetostring(publickey);
log.d("tag", "base64编码的公钥：" + encodepublic);
//获取私钥
byte[] privatekey = rsautils.getprivatekey(keypair);
log.d("tag", "私钥：" + stringutils.bytearraytostring(privatekey));
//私钥用base64编码
string encodeprivate = base64utils.encodetostring(privatekey);
log.d("tag", "base64编码的私钥：" + encodeprivate);
} catch (nosuchalgorithmexception e) {
e.printstacktrace();
}
其它
一、android加密的数据服务器上无法解密？
android的rsa加密方式是rsa/ecb/nopadding，而标准jdk是rsa/ecb/pkcs1padding，所以加密时要设置标准jdk的加密方式
二、base64编码。因为不同的设备对字符的处理方式不同，字符有可能处理出错，不利于传输。所以先把数据做base64编码，变成可见字符，减少出错
官方提供的base64类，base64.encode编码，base64.decode解码。用这个会有换行符，需要自定义
三、rsa是非对称加密算法。依赖于大数计算，加密速度比des慢，通常只用于加密少量数据或密钥
四、公钥加密比私钥加密块，公钥解密比私钥解密慢。加密后的数据大概是加密前的1.5倍
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。