java SHA1WithRSA 算法

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

public class RSA{
        
        public static final String  SIGN_ALGORITHMS = "SHA1WithRSA";
        
        /**
        * RSA签名
        * @param content 待签名数据
        * @param privateKey 商户私钥
        * @param input_charset 编码格式
        * @return 签名值
        */
        public static String sign(String content, String privateKey, String input_charset)
        {
        try 
        {
                PKCS8EncodedKeySpec priPKCS8    = new PKCS8EncodedKeySpec( Base64.decode(privateKey) ); 
                KeyFactory keyf                                 = KeyFactory.getInstance("RSA");
                PrivateKey priKey                               = keyf.generatePrivate(priPKCS8);

            java.security.Signature signature = java.security.Signature
                .getInstance(SIGN_ALGORITHMS);

            signature.initSign(priKey);
            signature.update( content.getBytes(input_charset) );

            byte[] signed = signature.sign();
            
            return Base64.encode(signed);
        }
        catch (Exception e) 
        {
                e.printStackTrace();
        }
        
        return null;
    }
        
        /**
        * RSA验签名检查
        * @param content 待签名数据
        * @param sign 签名值
        * @param ali_public_key 支付宝公钥
        * @param input_charset 编码格式
        * @return 布尔值
        */
        public static boolean verify(String content, String sign, String ali_public_key, String input_charset)
        {
                try 
                {
                        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
                byte[] encodedKey = Base64.decode(ali_public_key);
                PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));

                
                        java.security.Signature signature = java.security.Signature
                        .getInstance(SIGN_ALGORITHMS);
                
                        signature.initVerify(pubKey);
                        signature.update( content.getBytes(input_charset) );
                
                        boolean bverify = signature.verify( Base64.decode(sign) );
                        return bverify;
                        
                } 
                catch (Exception e) 
                {
                        e.printStackTrace();
                }
                
                return false;
        }
        
        /**
        * 解密
        * @param content 密文
        * @param private_key 商户私钥
        * @param input_charset 编码格式
        * @return 解密后的字符串
        */
        public static String decrypt(String content, String private_key, String input_charset) throws Exception {
        PrivateKey prikey = getPrivateKey(private_key);

        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, prikey);

        InputStream ins = new ByteArrayInputStream(Base64.decode(content));
        ByteArrayOutputStream writer = new ByteArrayOutputStream();
        //rsa解密的字节大小最多是128，将需要解密的内容，按128位拆开解密
        byte[] buf = new byte[128];
        int bufl;

        while ((bufl = ins.read(buf)) != -1) {
            byte[] block = null;

            if (buf.length == bufl) {
                block = buf;
            } else {
                block = new byte[bufl];
                for (int i = 0; i < bufl; i++) {
                    block[i] = buf[i];
                }
            }

            writer.write(cipher.doFinal(block));
        }

        return new String(writer.toByteArray(), input_charset);
    }

        
        /**
        * 得到私钥
        * @param key 密钥字符串（经过base64编码）
        * @throws Exception
        */
        public static PrivateKey getPrivateKey(String key) throws Exception {

                byte[] keyBytes;
                
                keyBytes = Base64.decode(key);
                
                PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
                
                KeyFactory keyFactory = KeyFactory.getInstance("RSA");
                
                PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
                
                return privateKey;
        }
}