R – How to combine n and e to create the public key in RSA

public-key-encryptionrsa

I have a 128-byte (1024-bit) modulus (in a byte array format) and my exponent (also in a byte array format). I need to create a 128-byte array representing the public key.

According to Wikipedia, "The public key consists of the modulus n and the public (or encryption) exponent e." But that doesn't tell me how to mix both.

What is the right operation to do?
– n^e (will that stay 128 bytes long?)
– just n?
– n followed by e?
– n added to e?
– something else?

Best Answer

You won't be able to create such an array. The "public key" has two parts: the exponent and the modulus. They are separate numbers that must be kept separate, since both are needed to perform encryption and decryption later on. Although your n is 1024 bits, the public key altogether is necessarily longer.

Related Solutions

C# RSA encryption using modulus and public exponent

Using RSACryptoServiceProvider

static public byte[] RSAEncrypt(byte[] data,
    RSAParameters keyInfo, 
    bool doOAEPPadding)
{
    byte[] encryptedData;
    using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
    {
        //Import the RSA Key information. This only needs
        //toinclude the public key information.
        rsa.ImportParameters(keyInfo);

        //Encrypt the passed byte array and specify OAEP padding.  
        //OAEP padding is only available on Microsoft Windows XP or later.  
        encryptedData = rsa.Encrypt(data, doOAEPPadding);
    }
    return encryptedData;       
}

So what you need are the RSAParameters but all you need to set are the Modulus and the Exponent to encrypt.

Git – How to access the SSH public key

cat ~/.ssh/id_rsa.pub or cat ~/.ssh/id_dsa.pub

You can list all the public keys you have by doing:

$ ls ~/.ssh/*.pub

Best Answer

Related Solutions

C# RSA encryption using modulus and public exponent

Git – How to access the SSH public key

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