Cryptography RC4

  • Thread starter Thread starter surcon
  • Start date Start date
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surcon

Hi everyone,

I would like to know whether .NET framework 2.0 provides support for
deriving an RC4 encryption key. Any suggestions would be greatly appreciated.
I have:

TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();
des.IV = new byte[8];
PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, new byte[0]);

When I try to create the object DES.key
des.Key = pdb.CryptDeriveKey("RC4", "MD5" 128, des.IV);

It throw the exception at this line that algorithm is not supported but
there is no problem if replacing RC4 by RC2.

Best Regards
 
Hi everyone,

I would like to know whether .NET framework 2.0 provides support for
deriving an RC4 encryption key. Any suggestions would be greatly appreciated.
I have:

TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();
des.IV = new byte[8];
PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, new byte[0]);

When I try to create the object DES.key
des.Key = pdb.CryptDeriveKey("RC4", "MD5" 128, des.IV);

It throw the exception at this line that algorithm is not supported but
there is no problem if replacing RC4 by RC2.

Best Regards
Click to expand...
From your code fragments, you appear to be deriving a DES key, not an
RC4 key: "des.Key = ...". You cannot use RC4 as the algname parameter
of CryptDeriveKey, the only allowed algorithms are DES, 3DES and RC2.
See http://blogs.msdn.com/shawnfa/archive/2004/04/14/113514.aspx for
more details.

RC4 is pretty flexible about the size of key it takes, the
specification allows keys up to 256 bytes long, with a default of 128
bytes. It should be possible to use a DES sized key with RC4.

The major question is why you want to use either DES or RC4, both are
rather old and rather broken. Neither can be considered secure at
present - better to use AES (=Rijndael), or if you need a stream
cypher then AES in CTR mode.

rossum
 
Lucky you!

Now there is a .NET managed-code implementation of the RC4 algorithm which is also compliant to Microsoft's Crypto API.

The project is called RC4ize.NET and is hosted at https://github.com/NeuronUpheaval/RC4ize.NET

Please feel free to check it out!

Cheers
Hi everyone,

I would like to know whether .NET framework 2.0 provides support for
deriving an RC4 encryption key. Any suggestions would be greatly appreciated.
I have:

TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();
des.IV = new byte[8];
PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, new byte[0]);

When I try to create the object DES.key
des.Key = pdb.CryptDeriveKey("RC4", "MD5" 128, des.IV);

It throw the exception at this line that algorithm is not supported but
there is no problem if replacing RC4 by RC2.

Best Regards
56:02 -0800, surcon

From your code fragments, you appear to be deriving a DES key, not an
RC4 key: "des.Key = ...". You cannot use RC4 as the algname parameter
of CryptDeriveKey, the only allowed algorithms are DES, 3DES and RC2.
See http://blogs.msdn.com/shawnfa/archive/2004/04/14/113514.aspx for
more details.

RC4 is pretty flexible about the size of key it takes, the
specification allows keys up to 256 bytes long, with a default of 128
bytes. It should be possible to use a DES sized key with RC4.

The major question is why you want to use either DES or RC4, both are
rather old and rather broken. Neither can be considered secure at
present - better to use AES (=Rijndael), or if you need a stream
cypher then AES in CTR mode.

rossum
Click to expand...
Click to expand...
 
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