Encrypt the summetric key using publickey and cipher Algorithm

Nagaveni Katari

3y1.1kASP.NET

Encrypt generated symmetric key of size 128 bits using banks public key with cipher algorithm Name/ MODE/ Padding for encryption using RSA / ECB / PKCS1Padding and convert the output to Base64 encoded string.

Public Key: a11b4f86cf186d127caa05db929d6f41

this is my code to generate symmetric key:

AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
aes.GenerateKey();
string aesKeyBase64 = Convert.ToBase64String(aes.Key);
return aesKeyBase64;

4 Replies

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Mohamed Azarudeen Z3y ago

Accepted answer

Hi nagaveni try this

using System;
using System.Security.Cryptography;
using System.Text;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Encodings;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Parameters;

public class Program
{
    public static void Main()
    {
        // Bank's public key
        string publicKey = "a11b4f86cf186d127caa05db929d6f41";

        // Generate the symmetric key
        AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
        aes.GenerateKey();
        byte[] aesKey = aes.Key;

        // Convert the symmetric key to Base64 string
        string aesKeyBase64 = Convert.ToBase64String(aesKey);

        // Encrypt the symmetric key using RSA with PKCS1Padding
        byte[] encryptedKey = EncryptWithRSA(aesKeyBase64, publicKey);

        // Convert the encrypted key to Base64 string
        string encryptedKeyBase64 = Convert.ToBase64String(encryptedKey);

        Console.WriteLine("Encrypted Symmetric Key: " + encryptedKeyBase64);
    }

    private static byte[] EncryptWithRSA(string plaintext, string publicKey)
    {
        // Convert the public key from hex to bytes
        byte[] publicKeyBytes = HexStringToByteArray(publicKey);

        // Initialize the RSA engine
        RsaKeyParameters rsaKeyParameters = new RsaKeyParameters(false, new Org.BouncyCastle.Math.BigInteger(1, publicKeyBytes), Org.BouncyCastle.Math.BigInteger.ValueOf(65537));
        RSAEngine rsaEngine = new RSAEngine();
        rsaEngine.Init(true, rsaKeyParameters);

        // Encrypt the plaintext with RSA
        byte[] plaintextBytes = Encoding.UTF8.GetBytes(plaintext);
        byte[] encryptedBytes = rsaEngine.ProcessBlock(plaintextBytes, 0, plaintextBytes.Length);

        return encryptedBytes;
    }

    private static byte[] HexStringToByteArray(string hexString)
    {
        int length = hexString.Length;
        byte[] bytes = new byte[length / 2];
        for (int i = 0; i < length; i += 2)
            bytes[i / 2] = Convert.ToByte(hexString.Substring(i, 2), 16);
        return bytes;
    }
}

Nagaveni Katari3y ago
Token will be passed by signing the constructed plain JSON string with clients Private Key and convert the output to Base64 encoded string using algorithm SHA1withRSA.

private key:65e365bd06f7f54a5282a63278bb21c2

json string: "{\"UserID\":\"1\",\"UserName\":\"Ayyappa\",\"txnId\":\"123456\",\"customerMob\":\"8569896857\",\"lname\":\"lakshman\",\"name\":\"Balasubbiramani\",\"mname\":\"ram\",\"productCode\":\"DMT\",\"address\":\"Mumbai\",\"dateOfBirth\":\"05/10/1982\",\"agentId\":\"CUSTOMER123456\",\"partnerId\":\"761\",\"kycStatus\":\"0\",\"pancardStatus\":\"0\",\"identityDocType\":\"0\",\"identityDocNo\":\"BgQkkDr14...\",\"channel\":\"4\",\"isOTPValidated\":\"0\",\"hashKey\":\"9f3f9eb0451e8c2e3955551c57458072\"}";

has key has to generate please give the solution for the problum
0
Nagaveni Katari3y ago
show another way
0

Amit Mohanty3y ago

To encrypt a generated symmetric key using a bank's public key with RSA encryption in ASP.NET, you can use the following code:

using System;
using System.Security.Cryptography;
using System.Text;

public static string EncryptSymmetricKeyWithRSA(string symmetricKey, string publicKey)
{
    byte[] aesKeyBytes = Convert.FromBase64String(symmetricKey);
    byte[] publicKeyBytes = HexStringToByteArray(publicKey);

    using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
    {
        rsa.ImportCspBlob(publicKeyBytes);

        byte[] encryptedBytes = rsa.Encrypt(aesKeyBytes, false);
        return Convert.ToBase64String(encryptedBytes);
    }
}

public static byte[] HexStringToByteArray(string hexString)
{
    if (hexString.Length % 2 != 0)
        throw new ArgumentException("Invalid hex string");

    byte[] byteArray = new byte[hexString.Length / 2];
    for (int i = 0; i < byteArray.Length; i++)
    {
        byteArray[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
    }

    return byteArray;
}

You can use the EncryptSymmetricKeyWithRSA method by passing your generated symmetric key and the bank's public key as parameters. The symmetricKey parameter should be in base64 string format, and the publicKey parameter should be the hex string representation of the bank's public key.

For example:

// Generate the symmetric key
AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
aes.GenerateKey();
byte[] aesKey = aes.Key;
// Convert the symmetric key to Base64 string
string symmetricKeyBase64 = Convert.ToBase64String(aesKey);
string publicKeyHex = "a11b4f86cf186d127caa05db929d6f41";
string encryptedSymmetricKey = EncryptSymmetricKeyWithRSA(symmetricKeyBase64, publicKeyHex);
Console.WriteLine(encryptedSymmetricKey);