I am using C# with .net core 3.1 on windows 10.
The option 1 in the following code successfully encrypts the plane bytes but the option 2 throw an error on Encrypt method. The only difference is the input bytes.
private byte[] TestCode()
{
var cert = new X509Certificate2("<PEM-FILE-WITH-CERTIFICATE>");
var publicKey = cert.GetRSAPublicKey();
var plainConnectionInfo1 = new PlainConnectionInfo()
{
ConnectionStringWithoutPath = "111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111",
Path = "222222222222"
};
byte[] encryptedBytes = null;
byte[] plainBytes = null;
var option = 1;
if (option == 1)
{
//Option 1
plainBytes = UTF8Encoding.UTF8.GetBytes(plainConnectionInfo1.ConnectionStringWithoutPath);
encryptedBytes = publicKey.Encrypt(plainBytes, RSAEncryptionPadding.OaepSHA256);
}
else
{
//Option 2
var plainConnectionInfo1Json = JsonConvert.SerializeObject(plainConnectionInfo1);
plainBytes = UTF8Encoding.UTF8.GetBytes(plainConnectionInfo1Json);
encryptedBytes = publicKey.Encrypt(plainBytes, RSAEncryptionPadding.OaepSHA256);
}
return encryptedBytes;
}
The only difference between option 1 and 2 is that there is a bit more text in the option 2 (compared to option 1). The option 2 is a json string where as it is just a string in option 1. Both strings were converted into UTF8 encoded bytes prior to encryption.
The option 2 throws following error at me:
Internal.Cryptography.CryptoThrowHelper.WindowsCryptographicException
HResult=0x80090027
Message=The parameter is incorrect.
Source=System.Security.Cryptography.Cng
StackTrace:
at System.Security.Cryptography.RSACng.EncryptOrDecrypt(SafeNCryptKeyHandle key, ReadOnlySpan`1 input, AsymmetricPaddingMode paddingMode, Void* paddingInfo, Boolean encrypt)
at System.Security.Cryptography.RSACng.EncryptOrDecrypt(Byte[] data, RSAEncryptionPadding padding, Boolean encrypt)
at System.Security.Cryptography.RSACng.Encrypt(Byte[] data, RSAEncryptionPadding padding)
Based on the error, I could not decipher as to what I am doing wrong. Can someone please explain?
I was using RSA public key with key size of 2048. With this key size, one could only encrypt 190 bytes at any time. This is explained fully here: https://crypto.stackexchange.com/questions/42097/what-is-the-maximum-size-of-the-plaintext-message-for-rsa-oaep
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