没有ASN.1编码的C＃RSA签名

Question

First of all, I need to replicate echo -n "someUnhashedData" | openssl pkeyutl -sign -inkey rsa.key | base64 -w 0 echo -n "someUnhashedData" | openssl pkeyutl -sign -inkey rsa.key | base64 -w 0 echo -n "someUnhashedData" | openssl pkeyutl -sign -inkey rsa.key | base64 -w 0 functionality in C# code. I managed to load private key into System.Security.Cryptography.RSACryptoServiceProvider and call SignData , but the result I'm getting is different from that of openssl pkeyutl .

As far as I understand, per this post and this RFC when pkeyutl -sign is called without -pkeyopt digest:hashFunc openssl does not bundle data with digest function identifier and skips ASN.1 encoding. This means that raw data is padded and encrypted. This tool seems to confirm that, decrypted signature looks like padded plaintext data.

So how do I do that with C#? All functions from RSACryptoServiceProvider require to specify hash algorithm and encode signature before encryption. Is there something I'm missing or will I have to write my own RSA private encryption?

Answer 1

.NET has no inbox API to performing "raw RSA". If you need that capability to match an existing bug in another RSA consumer you would have to make a new class which P/Invokes down to the system cryptographic libraries (or otherwise provides the functionality you seek)