Having looked at some of the information on RSA encryption modes, it would appear that PKCS#1 v1.5 (which you're using, because you're calling Decrypt(., false)) The two methods above InitRSAProvider and LoadRsaPublicKey were gotten out of tutorials to allow PEM keys as Strings to be used with. Private static bool CompareBytearrays(byte a, byte b) RSAParameters RSAKeyInfo = new RSAParameters() īyte pubkey = ReadFileKey(publicKeyFilePath, 'PUBLIC KEY', isFile) īyte SeqOID = Ĭount = bt // we already have the data sizeī(-1, SeekOrigin.Current) //last ReadByte wasn't a removed zero, so back up a byte Private static RSAParameters LoadRsaPublicKey(String publicKeyFilePath, Boolean isFile) RSACryptoServiceProvider rsa = InitRSAProvider(_publicKey) īyte bytes = Convert.FromBase64String(dataEncrypted) īyte decryptedBytes = rsa.Decrypt(bytes, true) RSAParameters _publicKey = LoadRsaPublicKey(publicKey, false) If (publicKey = null) throw new ArgumentNullException('publicKey') If (dataEncrypted = null) throw new ArgumentNullException('dataEncrypted')

public static string DecryptUsingPublic(string dataEncrypted, string publicKey) If I use rsa.Decrypt(bytes, false) I get a bad key exception. 'Error occurred while decoding OAEP padding.' This is my method (updated from my previous bad one as pointed out by Iridium) but when I try to decrypt the value I get an exception It would be great if there is some kind of reasonable solution besides begging them to change what they are doing. I am hoping someone might be able help me. I can't find a library to do it in any of the main languages I know i.e. I am told by the person sending me the value that this is no problem in PHP.

Am I being an idiot? Is this a normal thing to do? I can't seem to figure out how to do this. I am now being sent a value that is RSA encrypted using a private key which I am supposed to derive a usable value by decrypting using the public key. I also RSA sign and verify and have a reasonable understanding of how this all work I think. Net to decrypt using a private key, encrypt using a public key. Unfortunately despite my protests I have to do it, even though I know it makes little sense. I know the main answer I am likely to get is why the hell would you want to do that?!

Rsa private decrypt example