Error occurred while decoding OAEP padding

Question

in continuation of the http://stackoverflow.com/questions/949907/error-occurred-while-decoding-oaep-padding question

I have modified my code and now i am trying this code

CspParameters cspParam = new CspParameters();

cspParam = new CspParameters();

cspParam.Flags = CspProviderFlags.UseMachineKeyStore;

clsCertificates cc = new clsCertificates();

string a = "";

cc.OpenStoreIE(ref a);

cc.SetProperties();

X509Certificate2 cert = new X509Certificate2();

cert = cc.x509_2Cert;

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(cspParam);

//to gentrate private and public keys from the certificate

rsa.FromXmlString(cert.PublicKey.Key.ToXmlString(false));


String publicKey = rsa.ToXmlString(false); // gets the public key 
String privateKey = rsa.ToXmlString(true); // gets the private key working if paramter is false if true give error key is not valid for use in specified state

Response.Write("<Textarea rows=10 cols=100>PUBLIC: " + publicKey + "</TextArea>");

Response.Write("<Textarea rows=10 cols=100>PRIVATE: " + privateKey + "</Textarea>");

Response.Write("<BR>Encrypting the string \"HelloThere\" with the public Key:<BR>");

String str = "HelloThere";

RSACryptoServiceProvider RSA2 = new RSACryptoServiceProvider(cspParam);



//---Load the Public key---

RSA2.FromXmlString(publicKey);

//working with the folowing line instead of above but i need the keys of he certificte

//RSA2.ToXmlString(true);

Byte[] EncryptedStrAsByt = RSA2.Encrypt(System.Text.Encoding.Unicode.GetBytes(str), true);

String EncryptedStr = System.Text.Encoding.Unicode.GetString(EncryptedStrAsByt);

Response.Write("<Textarea rows=10 cols=100>Encrypted String: " + EncryptedStr + "</Textarea>");

Response.Write("<BR>Decrypting the Encrypted String with the Private key:<BR>");



RSACryptoServiceProvider RSA3 = new RSACryptoServiceProvider(cspParam);



//---Load the Private key---

RSA3.FromXmlString(privateKey);

//working with the folowing line instead of above but i need the keys of he certificte

//RSA3.ToXmlString(true);

Byte[] DecryptedStrAsByt = RSA3.Decrypt(EncryptedStrAsByt, true );//Error if true then error is error occured while decoding the OAE$P padding and if false then error is bad key i am using windows xp so it should be true.

String DecryptedStr = System.Text.Encoding.Unicode.GetString(DecryptedStrAsByt);

Response.Write("<Textarea rows=10 cols=100>Decrypted String: " + DecryptedStr + "</Textarea>");

The whole is working if i am not using the keys of digital certificate. but if the keys are of digital certificate eroors are there please help me urgently....

Answer 1

I found the solution My self.

Answer 2

Ya sure i am preapring an article on that and soon will publish it on my blog. the inital articles you can fin on my blog

Answer 3

A common mistake is to try to decrypt using the public key.

Answer 4

I ran into this exact problem. //UnicodeEncoding.GetBytes(...) is not always the inverse of UnicodeEncoding.GetString(...)

byte[] a = new byte[32];

RandomNumberGenerator gen = new RNGCryptoServiceProvider();

gen.GetBytes(a);

UnicodeEncoding byteConverter = new UnicodeEncoding();

byte[] b = byteConverter.GetBytes(byteConverter.GetString(a));

//byte array 'a' and byte array 'b' will not always contain the same elements.

This is why RSACryptoServiceProvider.Decrypt(...) fails.

A lot of encrypt/decrypt examples on the web use Unicode encoding. Do not use Unicode encoding.

Use Convert.FromBase64String and Convert.ToBase64String instead.

Answer 5

This error normally indicate you are using public key to decrypt, while you should use private key for decryption. Give it a try.