1、签名代码

/** 
 * 签名算法 
 */
public static final String SIGN_ALGORITHMS = "SHA1WithRSA";
/** 
 * RSA签名 
 * @param content   待签名数据 
 * @param privateKey 私钥 
 * @param encode 字符集编码 
 * @return 签名值 
 */  
  public static String sign(String content, String privateKey, String encode)   {  
    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(encode));  
     
          byte[] signed = signature.sign();                   
          return Base64.encode(signed);  
      } catch (Exception e)  {  
           e.printStackTrace();  
      }  
             
      return null;  
  }

2、验签代码

    /** 
     * 校验缓存控制文件的签名是否合法 
     * @param content  待签名数据
     * @param sign 签名值
     * @param publicKey 公钥
     * @return 失败时，返回false。
     */
     public static boolean verifySignature(String content,String sign,String publicKey){
         if(null == fileText || null == signText || "".equals(fileText) || "".equals(signText)){
             return false;
          }
          try {   
               byte[] pubKeyText = publicKey.getBytes();  
               byte[] signTextByte = signText.getBytes();    
               X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(Base64.decode(pubKeyText, Base64.DEFAULT));  
               KeyFactory keyFactory = KeyFactory.getInstance("RSA");    
               PublicKey pubKey = keyFactory.generatePublic(bobPubKeySpec);   
               byte[] signed = Base64.decode(signTextByte, Base64.DEFAULT);  
               Signature signatureChecker = Signature.getInstance("SHA1WithRSA");  
               signatureChecker.initVerify(pubKey);   
               signatureChecker.update(content.getBytes());   
               // 验证签名是否正常   
               return signatureChecker.verify(signed);
           } catch (Exception e) {
               MuLog.error(TAG, e);    
               return false;
           }
     }