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Cryptography Classes for .NET Compact Framework

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You may know that System.Security.Cryptography for Compact Framework lacks many cryptography algorithms compared to the desktop .Net Framework (2005 and later). In a project we have needed SHA512 encryption on Windows CE and we have found /cfAes library which provides almost all of the crypto functionality of .NET Framework. We are grateful to the author for sharing the class library.

The following table displays a comparison between the versions of .Net Framework with respect to the support for different crypyography algorithms (X means that it is supported, 0 means partially supported).

Crytpo Algorithm .NET 2003 OpenNETCF 1.2 /cfAES WSE 2.0 CF 2.0 .NET 2005
MD5 X X X X X
SHA1 X X X X X
SHA256 X X X
SHA384 X X X
SHA512 X X X
MACTripleDES X 0 X X
HMACSHA1 X X X X X
PasswordDeriveBytes X 0 X X
RC2 X X X X X
DES X X X X X
TripleDES X X X X X X
Rijndeal X X X X
RSA X X X X X X
DSA X X X X X
RIPEMD160 X X
HMACMD5 X X
HMACSHA256 X X
HMACSHA384 X X
HMACSHA512 X X
HMACRIPEMD160 X X
Rfc2898DeriveBytes X X
ProtectedData X X
ProtectedMemory X X
PSHA1 X X
AESKeyExchangeFormatter X X
TripleDesKeyExchangeFormatter X X
SecureString X X



You can download the source code of the library here.

Written by Volkan TUNALI

November 10th, 2010 at 11:56 am

Storage Cost over Years

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Every time I buy a new PC, either desktop or notebook, its hard disk capacity is larger than the previous one even though the total price of the PC is about equal. The same thing may apply for the other components of the PC like main memory capacity and CPU power, but hard disk capacity is something very different.

Matthew Komorowski has collected hard drive capacity/price data and created the graph below:

Storage cost over years
Source: http://www.mkomo.com/cost-per-gigabyte

Komorowski has also drawn a conclusion about the capacity/cost trend as:

Over the last 30 years, space per unit cost has doubled roughly every 14 months (increasing by an order of magnitude every 48 months)

Moreover, he has a formula for the cost as

cost = 10-0.2502(year-1980)+6.304

Below are two pictures from computer magazines of 80s. Incredible!

Written by Volkan TUNALI

September 18th, 2010 at 12:24 pm

Proof that P is not Equal to NP?

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Complexity ClassesFor a few days, everyone in the field of computer science has been talking about the manuscript P ≠ NP published by Vinay Deolalikar from HP Research Labs on August 6, 2010. The 102-page manuscript on the P versus NP problem has taken so much attention from computer science researchers like Scott Aaronson, Greg Baker, and Dick Lipton.

Let’s see what Wikipedia says about P ≠ NP as a refreshment for the subject:

The relationship between the complexity classes P (Polynomial time) and NP (Nondeterministic Polynomial time) is an unsolved problem in theoretical computer science, and is considered by many theoretical computer scientists to be the most important problem in the field.

A proof that showed that P ≠ NP, while lacking the practical computational benefits of a proof that P = NP, would also represent a very significant advance in computational complexity theory and provide guidance for future research. It would allow one to show in a formal way that many common problems cannot be solved efficiently, so that the attention of researchers can be focused on partial solutions or solutions to other problems. Due to widespread belief in P ≠ NP, much of this focusing of research has already taken place.

Yes, P ≠ NP is the expected answer, yet there is no accepted proof for that. It will be very interesting and lucky for us to witness an important milestone in computer science if Deolalikar’s claimed proof is found correct and approved by the computer science community. I think acceptance or rejection will take some time, and I’ll be waiting impatiently.


Update Jan 20th, 2011: Today I’ve seen a new work that claims P = NP with a Polynomial Algorithm for Boolean 3-Satisfiability Problem by Vladimir Romanov. http://romvf.wordpress.com/2011/01/19/open-letter/

Written by Volkan TUNALI

August 9th, 2010 at 5:45 pm