Use PEM encoded RSA private key in .NET

Question

I have a private key which looks like this: -----BEGIN RSA PRIVATE KEY----- Some private key data -----END RSA PRIVA I need to use this key in my C# project, but I couldn't find any example how to use key in this format. Thanks

Accepted Answer

- step 1 get "Some private key data" content.remove -----BEGIN RSA PRIVATE KEY----- and -----END RSA PRIVATE KEY-----, Removes all line symbols("
");

- step 2. parse key to RSA.

```
private RSACryptoServiceProvider CreateRsaProviderFromPrivateKey(string privateKey)
{
    var privateKeyBits = System.Convert.FromBase64String(privateKey);

var RSA = new RSACryptoServiceProvider();
    var RSAparams = new RSAParameters();

using (BinaryReader binr = new BinaryReader(new MemoryStream(privateKeyBits)))
    {
        byte bt = 0;
        ushort twobytes = 0;
        twobytes = binr.ReadUInt16();
        if (twobytes == 0x8130)
            binr.ReadByte();
        else if (twobytes == 0x8230)
            binr.ReadInt16();
        else
            throw new Exception("Unexpected value read binr.ReadUInt16()");

twobytes = binr.ReadUInt16();
        if (twobytes != 0x0102)
            throw new Exception("Unexpected version");

bt = binr.ReadByte();
        if (bt != 0x00)
            throw new Exception("Unexpected value read binr.ReadByte()");

RSAparams.Modulus = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.Exponent = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.D = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.P = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.Q = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.DP = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.DQ = binr.ReadBytes(GetIntegerSize(binr));
        RSAparams.InverseQ = binr.ReadBytes(GetIntegerSize(binr));
    }

RSA.ImportParameters(RSAparams);
    return RSA;
}

private int GetIntegerSize(BinaryReader binr)
{
    byte bt = 0;
    byte lowbyte = 0x00;
    byte highbyte = 0x00;
    int count = 0;
    bt = binr.ReadByte();
    if (bt != 0x02)
        return 0;
    bt = binr.ReadByte();

if (bt == 0x81)
        count = binr.ReadByte();
    else
        if (bt == 0x82)
        {
            highbyte = binr.ReadByte();
            lowbyte = binr.ReadByte();
            byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
            count = BitConverter.ToInt32(modint, 0);
        }
        else
        {
            count = bt;
        }

while (binr.ReadByte() == 0x00)
    {
        count -= 1;
    }
    binr.BaseStream.Seek(-1, SeekOrigin.Current);
    return count;
}
```

Use PEM encoded RSA private key in .NET

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