使用Java进行RSA加密/解密

Question

我正在使用Java中的RSA算法进行加密/解密的简单程序。我按如下方式创建了一个密码对象：

//Create a Cipher object
Cipher rsaCipher = Cipher.getInstance("RSA/ECB/NoPadding");

我通过调用加密函数进行加密：

String cipher=encrypt(textByte, pair, rsaCipher);
System.out.println("The Encryption using RSA Algorithm : "+cipher);

解密为：

//Decryption
String plain=decrypt(Base64.decodeBase64(cipher),pair, rsaCipher);
System.out.println("The Decryption using RSA Algorithm : "+plain);

当我显示输出时，解密输出在原始文本之前返回一个长空格：

但是，当我编辑用于创建Cipher对象的代码时：     //创建一个Cipher对象     密码rsaCipher = Cipher.getInstance（“RSA”）;

即，删除了操作模式和填充参数，问题得到解决，输出变为：

问题出在哪里。在第一种情况下（当空间出现时），我指定了NoPadding？为什么空格出现在解密的消息中？即使我使用填充，我希望这不应该发生。

修改 这是加密和解密方法：

public static String encrypt(byte[] textBytes, KeyPair pair, Cipher rsaCipher) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException
{
    //get the public key
    PublicKey pk=pair.getPublic(); 


    //Initialize the cipher for encryption. Use the public key.
    rsaCipher.init(Cipher.ENCRYPT_MODE, pk);

    //Perform the encryption using doFinal
    byte[] encByte = rsaCipher.doFinal(textBytes);

    // converts to base64 for easier display.
    byte[] base64Cipher = Base64.encodeBase64(encByte);

    return new String(base64Cipher);
}//end encrypt

public static String decrypt(byte[] cipherBytes, KeyPair pair, Cipher rsaCipher) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException
{
    //get the public key
    PrivateKey pvk=pair.getPrivate(); 

    //Create a Cipher object
    //Cipher rsaCipher = Cipher.getInstance("RSA/ECB/NoPadding");

    //Initialize the cipher for encryption. Use the public key.
    rsaCipher.init(Cipher.DECRYPT_MODE, pvk);

    //Perform the encryption using doFinal
    byte[] decByte = rsaCipher.doFinal(cipherBytes);

    return new String(decByte);

}//end decrypt

Answer 1

你的问题确实与填充有关。实际上，某些填充（PKCS＃1 1.5或OAEP填充）是安全RSA功能所必需的。此外，需要找到加密纯文本的开头和结尾。

RSA的模幂运算使用大整数执行。然后将这些操作的结果表示为八位字符串。这些八位字节串基本上是大端，无符号，整数的固定长度表示。这些整数用00个值填充（这在RSA标准中称为I2OS原语）。所以你看到的是模幂运算的结果，00填充仍然存在。

长话短说，总是使用填充方案。如今，OAEP将更为可取。将其与混合加密方案一起使用，或使用更高级别的容器格式，如CMS或PGP。

Answer 2

RSA的模幂运算使用大整数执行。然后将这些操作的结果表示为八位字符串。这些八位字节串基本上是大端，无符号，整数的固定长度表示。这些整数用00值字节填充（这在RSA标准中称为I2OS原语）。所以你看到的是模幂运算的结果，00填充仍然存在。

Answer 3

//This is a complete encryption and decryption module using 
//Algorithm: JWEAlgorithm.RSA_OAEP_256
//Encryption Method: A128CBC_HS256

public static String  encrypt(String text) throws Exception {
    // Set the plain text
    Payload payload = new Payload(text);
    // Create the header
    JWEHeader header = new JWEHeader(JWEAlgorithm.RSA_OAEP_256, EncryptionMethod.A128CBC_HS256);
    // Create the JWE object and encrypt it
    JWEObject jweObject = new JWEObject(header, payload);
    jweObject.encrypt(new RSAEncrypter(getPublicKey()));
    // Serialise to compact JOSE form...
    String jweString = jweObject.serialize();
    LOG.info("Generated Encrypted Key : {}", jweString);
    return jweString;
}

public static String decrypt(String text) throws Exception {
    // Parse into JWE object...
    JWEObject jweObject = JWEObject.parse(text);
    jweObject.decrypt(new RSADecrypter(getPrivateKey()));
    // Get the plain text
    Payload payload = jweObject.getPayload();
    System.out.println(payload.toString());
    return payload.toString();
}

private static RSAPublicKey getPublicKey() throws Exception {
    String filename = "/home/vaibhav/Setups/cert/pub.der";
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();

    X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return (RSAPublicKey) kf.generatePublic(spec);
}

private static RSAPrivateKey getPrivateKey() throws Exception {
    String filename = "/home/vaibhav/Setups/cert/private.pkcs8";
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();

    PKCS8EncodedKeySpec spec1 = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return (RSAPrivateKey) kf.generatePrivate(spec1);
}

Answer 4

希望这有帮助！ ：）

import java.util.*;
import java.math.*;
class  RSA
{
public static void main(String args[])
{
BigInteger one, p, q, E, D, n,P,Q;
Scanner s = new Scanner(System.in);
Scanner t = new Scanner(System.in);
System.out.println("Enter A's prime number!");
p =  s.nextBigInteger(); 
System.out.println("Enter B's prime number!");
q =  s.nextBigInteger();
n = p.multiply(q);
P = p.subtract(BigInteger.ONE);
Q =  q.subtract(BigInteger.ONE);
int x = 0;
do
{
System.out.println("Enter Public key ");
E =s.nextBigInteger();
if(((P.gcd(E)).equals(BigInteger.ONE))&&((Q.gcd(E)).equals(BigInteger.ONE)))
{x++;}
}while(x==0);
for(int i = 1;;i++)
{
D=new BigInteger(String.valueOf(i));
if(((D.multiply(E)).mod(P.multiply(Q))).equals(BigInteger.ONE))
break;
}
System.out.println("Enter Plain text!");
String in = "", out ="",  text = t.nextLine();
for(int i = 0;i < text.length();i++){
BigInteger T = new BigInteger(String.valueOf((int)(text.charAt(i)))), O, TF;
O = T.modPow(E,n);
out += (char)O.intValue();
TF = O.modPow(D,n);
in += (char)TF.intValue();
}
System.out.println("Encrypted text : " + out);
System.out.println("Decrypted text : "+ in);
}
}