> ## Documentation Index
> Fetch the complete documentation index at: https://devzone.nayax.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Security & Digital Signatures

> Implement RSA SHA-256 signatures for secure data entry.

Certain commands, such as `displayInput`, require a digital signature to ensure the integrity of the request.

### Key management

The client system is responsible for generating an **RSA SHA-256** private-public key pair.

* The **Private Key** must be maintained securely on your server.
* The **Public Key** is used by the VPOS to verify the request.

### C# implementation

Below is an example of how to sign a message and verify the signature using PKCS#1 padding.

```csharp C# theme={null}
static string SignMessage(string message, string privateKeyBase64)
{
    using (RSA rsa = ImportPrivateKey(privateKeyBase64))
    {
        byte[] messageBytes = Encoding.UTF8.GetBytes(message);
        byte[] signature = rsa.SignData(messageBytes, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
        return Convert.ToBase64String(signature);
    }
}

static bool VerifySignature(string message, string signatureBase64, string publicKeyBase64)
{
    using (RSA rsa = ImportPublicKey(publicKeyBase64))
    {
        byte[] messageBytes = Encoding.UTF8.GetBytes(message);
        byte[] signature = Convert.FromBase64String(signatureBase64);
        return rsa.VerifyData(messageBytes, signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
    }
}
```