Signature in PKCS1 v1.5: RSAPKCS1SignatureFormatter vs RSACryptoServiceProvider

Question

I need to sign a Hash value of data and get a digital signature in PKCS1 v1.5 format. My understanding is that RSAPKCS1SignatureFormatter.CreateSignature(HashValue) does exactly that. In other words, I calculate a Hash value, don't do anything
to it and just pass it to
CreateSignature(HashValue) and get a digital signature in PKCS1 v1.5 in result. Is that true?
Is this code the right way to achieve this?
int SignPKCS15PrivateKey(array<System::Byte>^ BinDataToSign, X509Certificate2^ Certificate, String^ ProviderName)
CspParameters^ cspa = gcnew CspParameters(1, ProviderName);
RSACryptoServiceProvider^ key = gcnew RSACryptoServiceProvider(cspa);
String^ privateKeyXML = Certificate->PrivateKey->ToXmlString(true);
key->FromXmlString(privateKeyXML);
//Get hash
SHA1Managed ^ sha1 = gcnew SHA1Managed();
array<Byte>^ Hash;
Hash = sha1->ComputeHash(BinDataToSign);
// Sign the hash
array<Byte>^ Signature;
RSAPKCS1SignatureFormatter^ RSAFormatter = gcnew RSAPKCS1SignatureFormatter(key);
RSAFormatter->SetHashAlgorithm("SHA1");
Signature = RSAFormatter->CreateSignature(Hash);
The problem is, when I use RSACryptoServiceProvider.SignHash() (in this case it is represented by
key variable = key.SignHash(....)), it returns exactly the same result as RSAPKCS1SignatureFormatter.CreateSignature(HashValue).
And they both pass this verification with a positive result:
//Verify signature
RSACryptoServiceProvider ^ PublicKey = safe_cast<RSACryptoServiceProvider ^>(Certificate->PublicKey->Key);
bool result1 = PublicKey->VerifyHash(Hash, CryptoConfig::MapNameToOID("SHA1"), Signature);
bool result2 = PublicKey->VerifyData(BinDataToSign, gcnew SHA1Managed(), Signature);
//Verify PKCS1.5 signature
RSAPKCS1SignatureDeformatter^ RSADeformatter = gcnew RSAPKCS1Signature Deformatter(PublicKey); //RSAPKCS1SignatureDeformatter(Certificate->PublicKey->Key);
RSADeformatter->SetHashAlgorithm("SHA1");
bool result3 = RSADeformatter->VerifySignature(Hash, Signature);
My question is:
1) does RSAPKCS1SignatureFormatter.CreateSignature()produce a signatures in PKCS1 v1.5
format?
2) What is the difference between signing with RSAPKCS1SignatureFormatter.CreateSignature() and RSACryptoServiceProvider.SignHash()?
Why would I choose one over the other, if they return the result in the same format?

Answer 1

Hello Andrius,
It seems that you are working with a C++ project, for this, i suggest that you could ask issues related with C++ development to C++ forum as:
https://social.msdn.microsoft.com/Forums/vstudio/en-US/home?forum=vcgeneral
There are C++ experts will help you.
Regards.
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