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@therightstuff

therightstuff/RSA.cs

Last active May 5, 2020
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Simple RSA Encryption, Decryption, signing and signature verification using Base64 encoded strings in C#
using System;
using System.Security.Cryptography;
using System.Text;
namespace MyProject.Data.Encryption
{
/* Encryption, decryption, signing and signature verification that's compatible with
* simple-free-encryption-tool
*/
public class RSA
{
public const bool OAEP_PADDING = true;
/// <summary>
/// PKCS1 padding is required for most encryption using JavaScript packages
/// </summary>
public const bool PKCS1_PADDING = false;
public static string Encrypt(
RSACryptoServiceProvider csp,
string plaintext
) {
return Convert.ToBase64String(
csp.Encrypt(
Encoding.UTF8.GetBytes(plaintext),
PKCS1_PADDING
)
);
}
public static string Decrypt(
RSACryptoServiceProvider csp,
string encrypted
) {
return Encoding.UTF8.GetString(
csp.Decrypt(
Convert.FromBase64String(encrypted),
PKCS1_PADDING
)
);
}
public static string Sign(
RSACryptoServiceProvider csp,
string plaintext
) {
// compute sha256 hash of the data
byte[] hash = new SHA256CryptoServiceProvider()
.ComputeHash(Encoding.UTF8.GetBytes(plaintext));
// base64 encode the signature
return Convert.ToBase64String(
csp.SignHash(hash, CryptoConfig.MapNameToOID("SHA256"))
);
}
public static bool Verify(
RSACryptoServiceProvider csp,
string plaintext,
string signature
) {
// compute sha256 hash of the data
byte[] hash = new SHA256CryptoServiceProvider()
.ComputeHash(Encoding.UTF8.GetBytes(plaintext));
return csp.VerifyHash(
hash,
CryptoConfig.MapNameToOID("SHA256"),
Convert.FromBase64String(signature));
}
public static void runTests(){
Console.WriteLine("Starting RSA tests");
string plaintext = "this is my secret message";
RSACryptoServiceProvider initialProvider = new RSACryptoServiceProvider(2048);
string encrypted = Encrypt(initialProvider, plaintext);
Console.WriteLine("plaintext encrypted to: " + encrypted);
string decrypted = Decrypt(initialProvider, encrypted);
Console.WriteLine("plaintext decrypted to: " + decrypted);
string signature = Sign(initialProvider, plaintext);
Console.WriteLine("signature: " + signature);
Console.WriteLine("signature verified: " + Verify(initialProvider, plaintext, signature));
// key and signature exported from simple-free-encryption-tool
string publicKey = @"-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA26+x8URoo0U5vk0Cs921
kVsqOnHYHs+YRiNuw64QIT/YnikCrEIqo3oEeH3Jt641LuplGiUPdQy3AaqvE2Dw
oiBHve0p1T/zGEMC9xTFdjIyD3eO0e9IROMZ3mAtbBqEYO6apG1yIoCh9lxPwZ0O
6FyKklpj1vZpw+GjnRMTPjoN/5TgEZ6RAZLYrRoKYS5b0GFMe5gLojTg+2PJ0pwk
OfSSIwJ+M4ngGPdIczKO3hxxJxWXOYvEsMuUzhUPPmi6nF+pv+6X10G9RpJpq2fd
nsodcxYx9YWA/2rLlvmLRmpH8plgRe83aHB1RIf5UNXgZWp7rsO7vf58rLFo2CQg
rQIDAQAB
-----END PUBLIC KEY-----";
signature = "LKeGxl2O8eXzkiYDbB5hO5NEUzde5ggqJPyLTTO2CtOD8ESnEhzm864mCMbhl0yxDccfN1g6r9DeG39g6O8A8Bx8JvHvuPaq8PNFz0jOU0v3CoNw8LKQUfJYzGRNHTQDRKk1kqIn+8+tJfhAbGceHlneCzMuEz6FoIDkwr8IKSxqkJpvKGmv2LRWGyjtpYNZf71B9EjjeCeyRBRmCcD2CKs/A2+tj4mWTxzs/+U9ik2BSR9fnBq0fcPzOCCgxtI9sYxqR650AnZONVHmozUO0M3dzgSfltrFORsVT4QFm0bbdZqDTsQnulfJPSHY3CIV85qA5OD7M6GM6tdLAAVl8A==";
RSACryptoServiceProvider importedProvider = RSAKeys.ImportPublicKey(publicKey);
Console.WriteLine("imported signature verified: " + Verify(importedProvider, plaintext, signature));
Console.WriteLine("RSA tests completed");
}
}
}
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