- Generating RSA key pair
- Creating a CSR file
- Generating a Checksum
- Encrypting with private key
- Reading a certificate file
- Verifying a signature
So while I was googling for hints, I came across this free library called OpenSSL.NET which looked promising. Find the code below which I use to accomplish the above tasks.
This function generates an RSA key pair and returns a CryptoKey object. The length of the keys are hard-coded to be 2048.
/// <summary>
/// Generates a 2048 bit RSA key pair.
/// </summary>
/// <returns>The key container</returns>
public static CryptoKey GenerateRsaKeyPair()
{
using(var rsa = new RSA())
{
rsa.GenerateKeys(2048, 0x10021, null, null);
return new CryptoKey(rsa);
}
}
The following function takes in a RSA key and creates a CSR file. I have used a DTO to pass in the additional details needed for the CSR generation.
/// <summary>
/// Generates a CSR file content according to the details given.
/// </summary>
/// <param name="csr">CSR details</param>
/// /// <param name="key">RSA key</param>
/// <returns>The CSR file content</returns>
public static string GenerateCsr(CsrProperties csr, CryptoKey key)
{
using (var subject = new X509Name
{
Country = csr.CountryName,
Organization = csr.OrganizationName,
OrganizationUnit = csr.OrganizationalUnitName,
SerialNumber = csr.SerialNumber,
Common = csr.CommonName
})
{
using (var req = new X509Request(0, subject, key))
{
return req.PEM;
}
}
}
For Checksum generation, which is also knowing as generating the hash, I used the following code. The algorithm was SHA256.
/// <summary>
/// Generates checksum using SHA256 algorithm.
/// </summary>
/// <param name="payLoad">Data to be used for hashing</param>
/// <returns>The hash</returns>
public static byte[] GenerateChecksum(byte[] payLoad)
{
using (var algo = new SHA256Managed())
{
return algo.ComputeHash(payLoad);
}
}
To do RSA encryption, I used .NET's native cryptography methods.
/// <summary>
/// Encrypts the data using RSA key.
/// </summary>
/// <param name="payLoad">Data to be encrypted</param>
/// <param name="key">RSA key</param>
/// <returns>The encrypted data</returns>
public static byte[] Encrypt(byte[] payLoad, CryptoKey key)
{
using (var rsa = key.GetRSA())
{
return rsa.PrivateEncrypt(payLoad, RSA.Padding.PKCS1);
}
}
Well that's about it for now. I will update this with more functions as I move on.
Cheers!
