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 02-18-2012, 01:01 AM #1 ybpark81 LQ Newbie   Registered: Jan 2012 Posts: 3 Rep: cryptography... what's difference between 8bits / 16 bits / 32 bits/ 64 bits/128bits? Hi, I have some question, is there anyone who can help me please? what's difference between 8bits / 16 bits / 32 bits/ 64 bits/128bits encryption password? How do you define each one? And where do you use them? Example: when i enter my password(which contain 8 characters) to enter my hotmail.com account, the password which i entered, is that 8bits? 16bits? 32bits? 64bits? or 128bit? and why?? 8 characters = 8 bytes = 64bits??? so am i using 64bits encryption password??? sorry to be so newbie... and thanks...
 02-18-2012, 04:04 PM #3 John VV LQ Muse   Registered: Aug 2005 Location: A2 area Mi. Posts: 17,523 Rep: the difference from 8 bit to 128 bit PRE-WW I to WW II pre1914 to 1940 wasn't the enigma a 128bit cypher
02-19-2012, 01:44 AM   #4
kuser:)
Member

Registered: Sep 2005
Location: Olsztyn, Poland
Distribution: Slackware 14.1
Posts: 168

Rep:
The following quotes are from this book:
"Principles of Computer Security: Security+ and Beyond"
Authors:
Wm. Artur Conklin, Gregory B. White, Chuck Cothren, Dwayne Williams, Roger L. Davis.
ISBN-13: 978-0-07-225643-7
ISBN-10: 0-07-225643-5

Chapter 5: Cryptography, pg. 80:
Quote:
 Key complexity is achieved by giving the key large number of possible values. The Keyspace is the size of every possible key value. When an algorithm lists a certain number of bits as a key, it is defining the key space.
[...]
Quote:
 Comparing a key made of 1 bit (2 possible values) and a key made of 1 letter (26 possible values) would not yield accurate results. Fortunately, the widespread use of computers have made almost all algorithms state their keyspace values in terms of bits. It is easy to see how key complexity affects an algorithm when you look at some of the encryption algorithms that have been broken. DES (Data Encryption Standard) used a 56-bit key, allowing 72,000,000,000,000,000 possible values, but it has been broken by modern computers.
And that's because of technological progress in computers' processing power (measured in FLoating-point Operations Per Second).
Quote:
 All encryption ciphers besides a "one-time pad" cipher are susceptible to a brute force attack-attempting every possible key. With a very small key, such as 2-bit key, trying every possible value is simple, as you only have four possibilities: 00, 01, 10, or 11. The 56-bit DES has 72 quadrillion values, and while that seems like a lot, computers have advanced to the extent that they can attempt billions of keys every second. This makes brute forcing a key only a matter of time, so large keys are required to make brute force attacks against the cipher take longer than the effective value of the information that is enciphered by them.
In other words, computers are becoming faster, so there is a need for larger keyspace (in bits). Brute force is just one of many types of password-cracking.

I hope I didn't violate the "fair use" rule of copyright law in my post...

Last edited by kuser:); 02-19-2012 at 01:59 AM.

 02-19-2012, 08:38 AM #5 sundialsvcs LQ Guru   Registered: Feb 2004 Location: SE Tennessee, USA Distribution: Gentoo, LFS Posts: 9,233 Blog Entries: 4 Rep: The Enigma cipher was a chained-transposition cipher with (almost-)simple incrementing fixed rotors. Other contemporary ciphers such as SIGABA increased security primarily by perturbing the rotor-positioning cycle. But none of these ciphers really had a sense of "bits." We do now know that German computers such as Konrad Zeus' seminal machines were at least considered for cryptographic purposes, but there simply aren't enough known records left after all that bombing. The key-length of a modern cipher is a rough measure of security against brute force attack, but only to the extent of the quality by which the algorithm in question actually uses the key. The "ideal" n-bit cipher would have exactly one key which produces the correct decryption and every other one produces an incorrect result that is "uselessly dissimilar to" the one and only right answer. But remember... the theoretical strength of a cipher's key is really a too-abstract notion of its actual, pragmatic security in practice. Most cryptosystems are broken due to attacks on the keying system. The pseudo-random number generator, for instance, might not be so random after all. The key might be known to consist of "printable" characters. The owner of the key might decide that he'd rather live a few more years, and to do so in possession both of his arms (or, more cravenly, "\$10 million dollars richer than before"), than to continue refusing to divulge the secret. And so on. Last edited by sundialsvcs; 02-19-2012 at 08:40 AM.

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