[SOLVED] How to convert this file to top-level statement?

Issue

This Content is from Stack Overflow. Question asked by Do Nhu Vy

using System;
using System.IO;
using System.Security.Cryptography;

public class HMACSHA512example
{

    public static void Main(string[] Fileargs)
    {
        string dataFile;
        string signedFile;
        //If no file names are specified, create them.
        if (Fileargs.Length < 2)
        {
            dataFile = @"text.txt";
            signedFile = "signedFile.enc";

            if (!File.Exists(dataFile))
            {
                // Create a file to write to.
                using (StreamWriter sw = File.CreateText(dataFile))
                {
                    sw.WriteLine("Here is a message to sign");
                }
            }
        }
        else
        {
            dataFile = Fileargs[0];
            signedFile = Fileargs[1];
        }
        try
        {
            // Create a random key using a random number generator. This would be the
            //  secret key shared by sender and receiver.
            byte[] secretkey = new Byte[64];
            //RNGCryptoServiceProvider is an implementation of a random number generator.
            using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider())
            {
                // The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey);

                // Use the secret key to sign the message file.
                SignFile(secretkey, dataFile, signedFile);

                // Verify the signed file
                VerifyFile(secretkey, signedFile);
            }
        }
        catch (IOException e)
        {
            Console.WriteLine("Error: File not found", e);
        }
    }  //end main
    // Computes a keyed hash for a source file and creates a target file with the keyed hash
    // prepended to the contents of the source file.
    public static void SignFile(byte[] key, String sourceFile, String destFile)
    {
        // Initialize the keyed hash object.
        using (HMACSHA512 hmac = new HMACSHA512(key))
        {
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                using (FileStream outStream = new FileStream(destFile, FileMode.Create))
                {
                    // Compute the hash of the input file.
                    byte[] hashValue = hmac.ComputeHash(inStream);
                    // Reset inStream to the beginning of the file.
                    inStream.Position = 0;
                    // Write the computed hash value to the output file.
                    outStream.Write(hashValue, 0, hashValue.Length);
                    // Copy the contents of the sourceFile to the destFile.
                    int bytesRead;
                    // read 1K at a time
                    byte[] buffer = new byte[1024];
                    do
                    {
                        // Read from the wrapping CryptoStream.
                        bytesRead = inStream.Read(buffer, 0, 1024);
                        outStream.Write(buffer, 0, bytesRead);
                    } while (bytesRead > 0);
                }
            }
        }
        return;
    } // end SignFile

    // Compares the key in the source file with a new key created for the data portion of the file. If the keys
    // compare the data has not been tampered with.
    public static bool VerifyFile(byte[] key, String sourceFile)
    {
        bool err = false;
        // Initialize the keyed hash object.
        using (HMACSHA512 hmac = new HMACSHA512(key))
        {
            // Create an array to hold the keyed hash value read from the file.
            byte[] storedHash = new byte[hmac.HashSize / 8];
            // Create a FileStream for the source file.
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                // Read in the storedHash.
                inStream.Read(storedHash, 0, storedHash.Length);
                // Compute the hash of the remaining contents of the file.
                // The stream is properly positioned at the beginning of the content,
                // immediately after the stored hash value.
                byte[] computedHash = hmac.ComputeHash(inStream);
                // compare the computed hash with the stored value

                for (int i = 0; i < storedHash.Length; i++)
                {
                    if (computedHash[i] != storedHash[i])
                    {
                        err = true;
                    }
                }
            }
        }
        if (err)
        {
            Console.WriteLine("Hash values differ! Signed file has been tampered with!");
            return false;
        }
        else
        {
            Console.WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }
    } //end VerifyFile
} //end class

Source: https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.hmacsha512?view=net-6.0

How to convert this file to top-level statement?



Solution

You just have to move your main to the top level, and keep the methods.

using System.Security.Cryptography;

string dataFile;
string signedFile;
//If no file names are specified, create them.
if (args.Length < 2)
{
    dataFile = @"text.txt";
    signedFile = "signedFile.enc";

    if (!File.Exists(dataFile))
    {
        // Create a file to write to.
        using (StreamWriter sw = File.CreateText(dataFile))
        {
            sw.WriteLine("Here is a message to sign");
        }
    }
}
else
{
    dataFile = args[0];
    signedFile = args[1];
}
try
{
    // Create a random key using a random number generator. This would be the
    //  secret key shared by sender and receiver.
    byte[] secretkey = new Byte[64];
    //RNGCryptoServiceProvider is an implementation of a random number generator.
    using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider())
    {
        // The array is now filled with cryptographically strong random bytes.
        rng.GetBytes(secretkey);

        // Use the secret key to sign the message file.
        SignFile(secretkey, dataFile, signedFile);

        // Verify the signed file
        VerifyFile(secretkey, signedFile);
    }
}
catch (IOException e)
{
    Console.WriteLine("Error: File not found", e);
}

// Computes a keyed hash for a source file and creates a target file with the keyed hash
// prepended to the contents of the source file.
static void SignFile(byte[] key, String sourceFile, String destFile)
{
    // Initialize the keyed hash object.
    using (HMACSHA512 hmac = new HMACSHA512(key))
    {
        using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
        {
            using (FileStream outStream = new FileStream(destFile, FileMode.Create))
            {
                // Compute the hash of the input file.
                byte[] hashValue = hmac.ComputeHash(inStream);
                // Reset inStream to the beginning of the file.
                inStream.Position = 0;
                // Write the computed hash value to the output file.
                outStream.Write(hashValue, 0, hashValue.Length);
                // Copy the contents of the sourceFile to the destFile.
                int bytesRead;
                // read 1K at a time
                byte[] buffer = new byte[1024];
                do
                {
                    // Read from the wrapping CryptoStream.
                    bytesRead = inStream.Read(buffer, 0, 1024);
                    outStream.Write(buffer, 0, bytesRead);
                } while (bytesRead > 0);
            }
        }
    }
    return;
} // end SignFile

// Compares the key in the source file with a new key created for the data portion of the file. If the keys
// compare the data has not been tampered with.
static bool VerifyFile(byte[] key, String sourceFile)
{
    bool err = false;
    // Initialize the keyed hash object.
    using (HMACSHA512 hmac = new HMACSHA512(key))
    {
        // Create an array to hold the keyed hash value read from the file.
        byte[] storedHash = new byte[hmac.HashSize / 8];
        // Create a FileStream for the source file.
        using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
        {
            // Read in the storedHash.
            inStream.Read(storedHash, 0, storedHash.Length);
            // Compute the hash of the remaining contents of the file.
            // The stream is properly positioned at the beginning of the content,
            // immediately after the stored hash value.
            byte[] computedHash = hmac.ComputeHash(inStream);
            // compare the computed hash with the stored value

            for (int i = 0; i < storedHash.Length; i++)
            {
                if (computedHash[i] != storedHash[i])
                {
                    err = true;
                }
            }
        }
    }
    if (err)
    {
        Console.WriteLine("Hash values differ! Signed file has been tampered with!");
        return false;
    }
    else
    {
        Console.WriteLine("Hash values agree -- no tampering occurred.");
        return true;
    }
} //end VerifyFile


This Question was asked in StackOverflow by Do Nhu Vy and Answered by ESG It is licensed under the terms of CC BY-SA 2.5. - CC BY-SA 3.0. - CC BY-SA 4.0.

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