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：

    1. openssl genrsa -out rsa_private_key.pem 1024
    2. openssl pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM -nocrypt -out private_key.pem
    3. 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

    1. <?php
    2. $private_key = '-----BEGIN RSA PRIVATE KEY-----
    3. MIICXQIBAAKBgQC3//sR2tXw0wrC2DySx8vNGlqt3Y7ldU9+LBLI6e1KS5lfc5jl
    4. TGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2klBd6h4wrbbHA2XE1sq21ykja/
    5. Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o2n1vP1D+tD3amHsK7QIDAQAB
    6. AoGBAKH14bMitESqD4PYwODWmy7rrrvyFPEnJJTECLjvKB7IkrVxVDkp1XiJnGKH
    7. 2h5syHQ5qslPSGYJ1M/XkDnGINwaLVHVD3BoKKgKg1bZn7ao5pXT+herqxaVwWs6
    8. ga63yVSIC8jcODxiuvxJnUMQRLaqoF6aUb/2VWc2T5MDmxLhAkEA3pwGpvXgLiWL
    9. 3h7QLYZLrLrbFRuRN4CYl4UYaAKokkAvZly04Glle8ycgOc2DzL4eiL4l/+x/gaq
    10. deJU/cHLRQJBANOZY0mEoVkwhU4bScSdnfM6usQowYBEwHYYh/OTv1a3SqcCE1f+
    11. qbAclCqeNiHajCcDmgYJ53LfIgyv0wCS54kCQAXaPkaHclRkQlAdqUV5IWYyJ25f
    12. oiq+Y8SgCCs73qixrU1YpJy9yKA/meG9smsl4Oh9IOIGI+zUygh9YdSmEq0CQQC2
    13. 4G3IP2G3lNDRdZIm5NZ7PfnmyRabxk/UgVUWdk47IwTZHFkdhxKfC8QepUhBsAHL
    14. QjifGXY4eJKUBm3FpDGJAkAFwUxYssiJjvrHwnHFbg0rFkvvY63OSmnRxiL4X6EY
    15. yI9lblCsyfpl25l7l5zmJrAHn45zAiOoBrWqpM5edu7c
    16. -----END RSA PRIVATE KEY-----';
    18. $public_key = '-----BEGIN PUBLIC KEY-----
    19. MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC3//sR2tXw0wrC2DySx8vNGlqt
    20. 3Y7ldU9+LBLI6e1KS5lfc5jlTGF7KBTSkCHBM3ouEHWqp1ZJ85iJe59aF5gIB2kl
    21. Bd6h4wrbbHA2XE1sq21ykja/Gqx7/IRia3zQfxGv/qEkyGOx+XALVoOlZqDwh76o
    22. 2n1vP1D+tD3amHsK7QIDAQAB
    23. -----END PUBLIC KEY-----';
    25. //echo $private_key;
    26. $pi_key =  openssl_pkey_get_private($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
    27. $pu_key = openssl_pkey_get_public($public_key);//这个函数可用来判断公钥是否是可用的
    28. print_r($pi_key);echo "\n";
    29. print_r($pu_key);echo "\n";
    32. $data = "aassssasssddd";//原始数据
    33. $encrypted = "";
    34. $decrypted = "";
    36. echo "source data:",$data,"\n";
    38. echo "private key encrypt:\n";
    40. openssl_private_encrypt($data,$encrypted,$pi_key);//私钥加密
    41. $encrypted = base64_encode($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
    42. echo $encrypted,"\n";
    44. echo "public key decrypt:\n";
    46. openssl_public_decrypt(base64_decode($encrypted),$decrypted,$pu_key);//私钥加密的内容通过公钥可用解密出来
    47. echo $decrypted,"\n";
    49. echo "---------------------------------------\n";
    50. echo "public key encrypt:\n";
    52. openssl_public_encrypt($data,$encrypted,$pu_key);//公钥加密
    53. $encrypted = base64_encode($encrypted);
    54. echo $encrypted,"\n";
    56. echo "private key decrypt:\n";
    57. openssl_private_decrypt(base64_decode($encrypted),$decrypted,$pi_key);//私钥解密
    58. echo $decrypted,"\n";