php服务端与客户端交互、提供开放api时，通常需要对敏感的部分api数据传输进行数据加密，这时候rsa非对称加密就能派上用处了，下面通过一个例子来说明如何用php来实现数据的加密解密

1、加密解密的第一步是生成公钥、私钥对，私钥加密的内容能通过公钥解密（反过来亦可以）

下载开源RSA密钥生成工具openssl（通常Linux系统都自带该程序），解压缩至独立的文件夹，进入其中的bin目录，执行以下命令：

openssl genrsa -out rsa_private_key.pem 1024
openssl pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM -nocrypt -out private_key.pem
openssl rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem

第一条命令生成原始 RSA私钥文件 rsa_private_key.pem，第二条命令将原始 RSA私钥转换为 pkcs8格式，第三条生成RSA公钥 rsa_public_key.pem
从上面看出通过私钥能生成对应的公钥，因此我们将私钥private_key.pem用在服务器端，公钥发放给android跟ios等前端

2、php中用生成的公钥、私钥进行加密解密，直接上代码

<?php  $private_key = '-----BEGIN RSA PRIVATE KEY-----  MIICXQIBAAKBgQC3//sR2tXw0wrC2DySx8vNGlqt3Y7ldU9+LBLI6e1KS5lfc5jl  TGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2klBd6h4wrbbHA2XE1sq21ykja/  Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o2n1vP1D+tD3amHsK7QIDAQAB  AoGBAKH14bMitESqD4PYwODWmy7rrrvyFPEnJJTECLjvKB7IkrVxVDkp1XiJnGKH  2h5syHQ5qslPSGYJ1M/XkDnGINwaLVHVD3BoKKgKg1bZn7ao5pXT+herqxaVwWs6  ga63yVSIC8jcODxiuvxJnUMQRLaqoF6aUb/2VWc2T5MDmxLhAkEA3pwGpvXgLiWL  3h7QLYZLrLrbFRuRN4CYl4UYaAKokkAvZly04Glle8ycgOc2DzL4eiL4l/+x/gaq  deJU/cHLRQJBANOZY0mEoVkwhU4bScSdnfM6usQowYBEwHYYh/OTv1a3SqcCE1f+  qbAclCqeNiHajCcDmgYJ53LfIgyv0wCS54kCQAXaPkaHclRkQlAdqUV5IWYyJ25f  oiq+Y8SgCCs73qixrU1YpJy9yKA/meG9smsl4Oh9IOIGI+zUygh9YdSmEq0CQQC2  4G3IP2G3lNDRdZIm5NZ7PfnmyRabxk/UgVUWdk47IwTZHFkdhxKfC8QepUhBsAHL  QjifGXY4eJKUBm3FpDGJAkAFwUxYssiJjvrHwnHFbg0rFkvvY63OSmnRxiL4X6EY  yI9lblCsyfpl25l7l5zmJrAHn45zAiOoBrWqpM5edu7c  -----END RSA PRIVATE KEY-----';    $public_key = '-----BEGIN PUBLIC KEY-----  MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC3//sR2tXw0wrC2DySx8vNGlqt  3Y7ldU9+LBLI6e1KS5lfc5jlTGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2kl  Bd6h4wrbbHA2XE1sq21ykja/Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o  2n1vP1D+tD3amHsK7QIDAQAB  -----END PUBLIC KEY-----';    //echo $private_key;  $pi_key =  openssl_pkey_get_private($private_key);//这个函数可用来判断私钥是否是可用的，可用返回资源id Resource id  $pu_key = openssl_pkey_get_public($public_key);//这个函数可用来判断公钥是否是可用的  print_r($pi_key);echo "\n";  print_r($pu_key);echo "\n";      $data = "aassssasssddd";//原始数据  $encrypted = "";   $decrypted = "";     echo "source data:",$data,"\n";    echo "private key encrypt:\n";    openssl_private_encrypt($data,$encrypted,$pi_key);//私钥加密  $encrypted = base64_encode($encrypted);//加密后的内容通常含有特殊字符，需要编码转换下，在网络间通过url传输时要注意base64编码是否是url安全的  echo $encrypted,"\n";    echo "public key decrypt:\n";    openssl_public_decrypt(base64_decode($encrypted),$decrypted,$pu_key);//私钥加密的内容通过公钥可用解密出来  echo $decrypted,"\n";    echo "---------------------------------------\n";  echo "public key encrypt:\n";    openssl_public_encrypt($data,$encrypted,$pu_key);//公钥加密  $encrypted = base64_encode($encrypted);  echo $encrypted,"\n";    echo "private key decrypt:\n";  openssl_private_decrypt(base64_decode($encrypted),$decrypted,$pi_key);//私钥解密  echo $decrypted,"\n";