通过 OpenSSL 从 BouncyCastle 的加密字符串解密字符串的问题

Question

I am using BouncyCastle and C# to crypt a string with RSA engine and a public key.

I want to decrypt the string by OpenSSL (Linux) and the private key by terminal; actually by OpenSSL library but I have problems by commands terminal too.

I created the keys by OpenSSL commands

openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048

I have issues to decrypt the string by OpenSSL, I wrote a stub for crypt a file.

This is the stub of the crypting

  public static void CryptStringByPublicKey(string stringToCrypt)
        {

            var key = GetPublicKey();

            var e = new Pkcs1Encoding(new RsaEngine());

            e.Init(true, key);

            var bytes = Encoding.ASCII.GetBytes(stringToCrypt);

            var encryptedBytes = e.ProcessBlock(bytes, 0, bytes.Length);

            // Which Encoding?
            var stringToSave = Encoding.UTF8.GetString(encryptedBytes);

            File.WriteAllText(@"C:\temp\encrypted_file", stringToSave);



        }

        public static RsaKeyParameters GetPublicKey()
        {

            const string privateKeyString = @"C:\temp\public_key.pem";


            RsaKeyParameters publicKey;

            using (var reader = File.OpenText(privateKeyString))
                publicKey = (RsaKeyParameters)new PemReader(reader).ReadObject();

            return publicKey;
        }

This is the commands line on Linux to decrypt

openssl rsautl -decrypt -in encrypted_file -out message.decrypted -inkey lora_private.pem 

I expected the decrypted string in message.decrypted but openssl respond

140251030225344:error:0406506C:rsa routines:rsa_ossl_private_decrypt:data greater than mod len:../crypto/rsa/rsa_ossl.c:399:

I tried to figure problems in encoding the char array, I tried all kinds of encoding (UTF8, ASCII).

Someone can help me with any suggestions?

Answer 1

Can't comment as too new.

Try encrypting as base64 before sending if you must send as text. I have done this in reverse (php openssl --> c#)

Then remove the spaces.

byte[] encryptedBytes = Convert.FromBase64String(encrypted.Replace(" ", "+"));

Answer 2

I had forgot that my encrypted bytes were base64 encoded. OpenSSL will happily decode your base64 string for you, and you can make a nice one-liner. DON'T forget the -A option:

openssl.exe base64 -A -d -in enc64.txt | openssl.exe pkeyutl -decrypt -inkey .\keys\privatekey.pem