How to do encrypt and decrypt data using Cryptography API Next Generation (CNG) in C#?

Question

Hi Team,
How to implement encrypt and decrypt mechanism using CNG ( Cryptography API Next Generation) in C#.Net?

below link about CNG:
https://learn.microsoft.com/en-us/windows/win32/seccng/about-cng

Please help me on this.

Regards,
Prabhakaran

Answer 1

Hi @Prabs ,
I made some simplifications and modifications on the previous example, and it can now run correctly.
You can refer to the following code.

        public string Encrypt(string PlainText, String Salt = "Kosher", String InitialVector = "OFRna73m*aze01xY")  
        {  
            if (string.IsNullOrEmpty(PlainText))  
            {  
                return string.Empty;  
            }  
            SHA256Managed sHA256Managed = new SHA256Managed();  
            byte[] key = sHA256Managed.ComputeHash(Encoding.ASCII.GetBytes(Salt));  
            byte[] iv = Encoding.ASCII.GetBytes(InitialVector);  
  
            using (var SymmetricKey = new AesCng()  
            {  
                Key = key,  
                IV = iv,  
                KeySize = 256,  
                BlockSize = 128,  
                Mode = CipherMode.CBC,  
            })  
            {  
                using (var transform = SymmetricKey.CreateEncryptor(key, iv))  
                {  
                    var inputBytes = Encoding.UTF8.GetBytes(PlainText);  
                    var encryptedBytes = transform.TransformFinalBlock(inputBytes, 0, inputBytes.Length);  
                    return Convert.ToBase64String(encryptedBytes);  
                }  
            }  
        }  
  
        public string Decrypt(string CipherText, String Salt = "Kosher", String InitialVector = "OFRna73m*aze01xY")  
        {  
            if (string.IsNullOrEmpty(CipherText))  
            {  
                return string.Empty;  
            }  
            SHA256Managed sHA256Managed = new SHA256Managed();  
            byte[] key = sHA256Managed.ComputeHash(Encoding.ASCII.GetBytes(Salt));  
            byte[] iv = Encoding.ASCII.GetBytes(InitialVector);  
  
            using (var SymmetricKey = new AesCng()  
            {  
                Key = key,  
                IV = iv,  
                KeySize = 256,  
                BlockSize = 128,  
                Mode = CipherMode.CBC,  
            })  
            {  
                using (var transform = SymmetricKey.CreateDecryptor(key, iv))  
                {  
                    var inputBytes = Convert.FromBase64String(CipherText);  
                    var PlainTextBytes = transform.TransformFinalBlock(inputBytes, 0, inputBytes.Length);  
                    return Encoding.UTF8.GetString(PlainTextBytes);  
                }  
            }  
        }  

Hope the code above colud be helpful.
Best Regards.
Jiachen Li

----------

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Answer 2

Hi @Prabs ,
Here is a test example of AesCng https://github.com/er0dr1guez/corefx/blob/master/src/System.Security.Cryptography.Cng/tests/InvasiveCngTests.cs.
And here is an implementation case of AesCng encryption and decryption which you can refer to.

        private String Encrypt_String_By_AesCng_Engine02(String PlainText,  
                             String Password,  
                              String Salt = "Kosher",  
                             String HashAlgorithm = "SHA1",  
                             int PasswordIterations = 2,  
                             String InitialVector = "OFRna73m*aze01xY",  
                             int KeySize = 256)  
        {  
        if (String.IsNullOrEmpty(PlainText)) return "";  
            byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);  
            byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);  
            byte[] PlainTextBytes = Encoding.UTF8.GetBytes(PlainText);  
            PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);  
            SHA256Managed sHA256Managed = new SHA256Managed();  
            byte[] KeyBytes = sHA256Managed.ComputeHash(Encoding.Unicode.GetBytes(Password));  
  
        AesCng SymmetricKey = new AesCng();  
            SymmetricKey.Mode = CipherMode.CBC;  
            byte[] CipherTextBytes;  
            using (ICryptoTransform Encryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes))  
            {  
                using (MemoryStream MemStream = new MemoryStream())  
                {  
                    using (CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write))  
                    {  
                        CryptoStream.Write(PlainTextBytes, 0, PlainTextBytes.Length);  
                        CryptoStream.FlushFinalBlock();  
                        CipherTextBytes = MemStream.ToArray();  
                        MemStream.Close();  
                        CryptoStream.Close();  
                    }  
                }  
            }  
            SymmetricKey.Clear();  
        return Convert.ToBase64String(CipherTextBytes);  
        }  
  
        private String Decrypt_String_By_AesCng_Engine02(String CipherText,  
                     String Password,  
                      String Salt = "Kosher",  
                     String HashAlgorithm = "SHA1",  
                     int PasswordIterations = 2,  
                     String InitialVector = "OFRna73m*aze01xY",  
                     int KeySize = 256)  
        {  
            if (String.IsNullOrEmpty(CipherText))return "";  
            byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);  
            byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);  
            byte[] CipherTextBytes = Convert.FromBase64String(CipherText);  
            PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);  
            SHA256Managed sHA256Managed = new SHA256Managed();  
            byte[] KeyBytes = sHA256Managed.ComputeHash(Encoding.Unicode.GetBytes(Password));  
  
            AesCng SymmetricKey = new AesCng();  
            SymmetricKey.Mode = CipherMode.CBC;  
            byte[] PlainTextBytes = new byte[CipherTextBytes.Length - 1];  
            int ByteCount = 0;  
  
            using (ICryptoTransform Decryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes))  
            {  
                using (MemoryStream MemStream = new MemoryStream(CipherTextBytes))  
                {  
                    using (CryptoStream CryptoStream = new CryptoStream(MemStream, Decryptor, CryptoStreamMode.Read))  
                    {  
                        ByteCount = CryptoStream.Read(PlainTextBytes, 0, PlainTextBytes.Length);  
                        MemStream.Close();  
                        CryptoStream.Close();  
                    }  
                }  
            }  
            SymmetricKey.Clear();  
            return Encoding.UTF8.GetString(PlainTextBytes, 0, ByteCount);  
        }  

Hope the code above colud be helpful.
Best Regards.
Jiachen Li

----------

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Answer 3

Hi @Prabs ,

How to implement encrypt and decrypt mechanism using CNG ( Cryptography API Next Generation) in C#.Net?

You can refer to the following two documents.
https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.aescng provides a CNG implementation of the Aes algorithm(SymmetricAlgorithm).
https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.rsacng provides a CNG implementation of the RSA algorithm(AsymmetricAlgorithm).
Hope the documents could be helpful.
Best Regards.
Jiachen Li

----------

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Answer 4

You can refer to https://learn.microsoft.com/en-us/windows/win32/seccng/encrypting-data-with-cng