RSA解密错误 - IllegalBlockSizeException:数据不得超过128个字节

Question

我现在正在制作RSA消息认证软件.过程如下:

1. 使用A的私钥(1024位)对邮件进行签名
2. 使用A的公钥验证邮件(1024位)

#1代码(如下)工作正常并生成以下结果:

5554c9a9f6838b6cf40d9dbfbab3d90ea27aa6434ed095d289c13c2624617993ad99161ac265276d150510c176341d8ab8600d08b7353286d465e6bd3370a6fd8dd3ffb82916f612fd6dcee5e654ed801cfca6b6d2d5d6dc99ff7921b615abdf62eb67db1f71e6a6ea70012fd35e7cefa1a8d3aab7614c47746cfe1fc2bc875b

但是#2代码显示以下错误:

javax.crypto.IllegalBlockSizeException: Data must not be longer than 128 bytes

我认为#1中的行Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 产生2048位(256字节)的结果.也许这就是问题......记住我使用1024位私钥.

那么#1代码如何生成128字节的结果呢？

1. SignMail.java

public class SignMail {

    static {
        Security.addProvider(new org.spongycastle.jce.provider.BouncyCastleProvider());
    }

    public static String sign(String userOriginalMessage) throws Exception {

        PEMReader userPrivateKey = new PEMReader(
          new InputStreamReader(
             new FileInputStream(Environment.getExternalStorageDirectory()+"/pkcs10priv.key")));

        KeyPair keyPair = (KeyPair)userPrivateKey.readObject();

        byte[] cipherText;
        //modified by JEON 20130817
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        //encrypt the message using private key
        cipher.init(Cipher.ENCRYPT_MODE, keyPair.getPrivate());
        cipherText = cipher.doFinal(userOriginalMessage.getBytes());
        return new String(Hex.encode(cipherText));

    }


}

2. UserSMSVerifier.java

public class UserSMSVerifier {

static String signedMail;

static {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
}


public static String messageGenarator(
        String UserCert,
        String origninalMessage         
        ) throws Exception{

    InputStream userCertStream = new ByteArrayInputStream(UserCert.getBytes("UTF-8"));

    PEMReader userCerti = new PEMReader(
              new InputStreamReader(
                      userCertStream));



    //KeyPair userPrivate = (KeyPair)userPrivateKey.readObject();
    X509Certificate userCert = (X509Certificate)userCerti.readObject();


    byte[] dectyptedText = null;
    // decrypt the text using the private key
    //modified by JEON 20130817
    //Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    cipher.init(Cipher.DECRYPT_MODE, userCert.getPublicKey());
    dectyptedText = cipher.doFinal(origninalMessage.getBytes());

    String result = new String(dectyptedText, Charset.forName("UTF-8"));
    return result;

}


}

#2代码由以下JSP执行

#3 messageVeri.JSP

<%@ page language="java" contentType="text/html; charset=euc-kr" %>

<%@ page session = "true" %>

<%@ page import="java.sql.DriverManager" %>
<%@ page import="java.sql.Connection" %>
<%@ page import="java.sql.PreparedStatement" %>
<%@ page import="java.sql.Statement" %>
<%@ page import="java.sql.SQLException" %>
<%@ page import="java.sql.ResultSet" %>

<%@ page import="myPackage.UserSMSVerifier" %>


<%
    request.setCharacterEncoding("euc-kr");

    String userID = request.getParameter("sender");
    String encryptedSMS = request.getParameter("encryptedSMS");

    //String sql = "select user_id, user_pw from testca.testca_init where user_id=? and user_pw=?";
    //String sql = "update testca.testca_init set pkcs10request = '"+pkcs10request_new+"' where user_id='user1'";
    String sql = "select * from testca.testca_init where user_id='" + userID + "'";

    Class.forName("com.mysql.jdbc.Driver");

    Connection conn = null;
    PreparedStatement pstmt = null;

    Statement stmt = null;
    ResultSet rs = null;

    String jdbcDriver = "jdbc:mysql://localhost:3306/";
    String dbUser = "root";
    String dbPass = "fo.......t";


    try{
        conn = DriverManager.getConnection(jdbcDriver, dbUser, dbPass);
        stmt = conn.createStatement();
        //stmt.executeUpdate(sql);
        rs=stmt.executeQuery(sql);
        while(rs.next()){
        //rs=stmt.executeQuery(sql);
        String userCertificate=rs.getString("certificate");
        UserSMSVerifier.messageGenarator(userCertificate, encryptedSMS);
        }



    }catch(Exception ex){out.print("Error 2: " +ex);}
    /*
    if(rs.next())
    {
        //session.setAttribute("userID", userID);
        out.print("Insert Succeed!");
        out.println();
        //out.print("Welcome!" + " " + session.getAttribute("userID"));
    }
    else
    {
        out.print("failed to login!");
        //session.invalidate();
    }
    */

%>

Answer 1

您的签名字符串包含256个字符,但这是十六进制的,实际上代表128 个字节.

在验证签名之前,必须将其转换回字节数组.这不是someString.getBytes()通过DatatypeConverter.parseHexBinary(someString)(或通过您喜欢的任何其他方法)来实现的.

此外,我强烈建议您在签名邮件时使用Signature类而不是Cipher类.目前,您的代码只能处理长度小于128字节的消息(实际上,由于填充较小).相反,您应该在签名之前对消息进行散列(例如,使用该SHA256withRSA机制).