Text File Signing using PKCS#7 Signature in C#

Question

How to encrypt and decrypt the text file in c# insted of JAVA. Can anyone help me to do in C#?

Amit Mohanty · Answer

Check this: using System; using System.IO; using System.Security.Cryptography; using System.Text; public class FileEncryption { public static void EncryptFile(string inputFile, string outputFile, X509Certificate2 recipientCertificate) { ContentInfo contentInfo = new ContentInfo(File.ReadAllBytes(inputFile)); EnvelopedCms envelopedCms = new EnvelopedCms(contentInfo); CmsRecipient recipient = new CmsRecipient(recipientCertificate); envelopedCms.Encrypt(recipient); byte[] encryptedBytes = envelopedCms.Encode(); File.WriteAllBytes(outputFile, encryptedBytes); } public static void DecryptFile(string inputFile, string outputFile, X509Certificate2 recipientCertificate) { byte[] encryptedBytes = File.ReadAllBytes(inputFile); EnvelopedCms envelopedCms = new EnvelopedCms(); envelopedCms.Decode(encryptedBytes); envelopedCms.Decrypt(new X509Certificate2Collection(recipientCertificate)); byte[] decryptedBytes = envelopedCms.ContentInfo.Content; File.WriteAllBytes(outputFile, decryptedBytes); } } // how to use string inputFile = "path/to/input.txt"; string encryptedFile = "path/to/encrypted.p7"; string decryptedFile = "path/to/decrypted.txt"; // Load the recipient certificate X509Certificate2 recipientCertificate = new X509Certificate2("path/to/recipient.pfx", "certificatePassword"); FileEncryption1.EncryptFile(inputFile, encryptedFile, recipientCertificate); FileEncryption1.DecryptFile(encryptedFile, decryptedFile, recipientCertificate); Console.WriteLine("Encryption and decryption completed successfully!");

Imap Backup · Answer

thanks

ashid das · Answer

Hi Mohamed Azarudeen, It is showing below error.

ashid das · Answer

Hi Mohamed Azarudeen, Please share how to decrypt that encrypted file.

Mohamed Azarudeen Z · Answer

using System; using System.IO; using System.Security.Cryptography; using System.Security.Cryptography.Pkcs; using System.Security.Cryptography.X509Certificates; using System.Text; class Program { static void Main() { // Step 1: Load the PKCS#12 keystore (pfx file) and get the private key string pfxPath = "path/to/your/certificate.pfx"; string pfxPassword = "your-pfx-password"; X509Certificate2 certificate = new X509Certificate2(pfxPath, pfxPassword, X509KeyStorageFlags.Exportable); RSACryptoServiceProvider privateKey = (RSACryptoServiceProvider)certificate.PrivateKey; // Step 2: Specify the signature algorithm string signatureAlgorithm = "SHA256"; // Step 3: Read the original file string filePath = "path/to/your/original/file.txt"; byte[] originalData = File.ReadAllBytes(filePath); // Step 4: Create a SignedCms object to generate the PKCS#7 signature ContentInfo contentInfo = new ContentInfo(originalData); SignedCms signedCms = new SignedCms(contentInfo, true); // Step 5: Create a signer with the private key and signature algorithm CmsSigner signer = new CmsSigner(privateKey); signer.DigestAlgorithm = new Oid(signatureAlgorithm); // Step 6: Initiate the signature signedCms.ComputeSignature(signer); // Step 7: Get the signature bytes byte[] signature = signedCms.Encode(); // Step 8: Convert the signature bytes to Base64 string base64Signature = Convert.ToBase64String(signature); // Step 9: Encode the original file to Base64 string base64OriginalFile = Convert.ToBase64String(originalData); // Step 10: Extract the public key certificate and encode it to Base64 string base64PublicKeyCertificate = Convert.ToBase64String(certificate.RawData); // Now you have the base64Signature, base64OriginalFile, and base64PublicKeyCertificate. // You can use them as needed for further processing or verification. // Example: Save the signed data to a new file string signedFilePath = "path/to/your/signed/file.txt"; File.WriteAllText(signedFilePath, $"{base64Signature}
{base64OriginalFile}
{base64PublicKeyCertificate}"); } } Hi Ashid you can use the .NET Framework's cryptography libraries to achieve text file signing using a PKCS#7 signature. Here's the equivalent C# code for the steps involved in signing: