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FEATURE
Hashing for Security
A first look at cryptographic hash functions
Issue: 9.2 (January/February 2011)
Author: JC Cruz
Author Bio: JC is a freelance engineering writer from North Vancouver, British Columbia. He frequently contributes articles to MacTech and REALbasic Developer. He also wrote for the now defunct Python Magazine, and is now working on a database e-book. Away from the writing pile, JC spends quality time with his charming foster nephew. He can be reached at
Article Description: No description available.
Article Length (in bytes): 43,110
Starting Page Number: 47
Article Number: 9208
Resource File(s):
9208project.zip Updated: 2011-01-06 10:03:25
Related Web Link(s):
http://en.wikipedia.org/wiki/Circular_shift
http://www.faqs.org/rfcs/rfc1321.html
http://www.faqs.org/rfcs/rfc3174.html
http://csrc.nist.gov/publications/fips/fips180-3/fips180-3_final.pdf
http://en.wikipedia.org/wiki/SHA-2
http://en.wikipedia.org/wiki/MD5
http://en.wikipedia.org/wiki/SHA-2
http://en.wikipedia.org/wiki/SHA-1
http://en.wikipedia.org/wiki/Whirlpool_
http://en.wikipedia.org/wiki/Merkle%E2%80%93Damg%C3%A5rd_construction
http://en.wikipedia.org/wiki/Cryptographic_hash_function
Excerpt of article text...
The last time we looked at hash functions, we learned that these functions fall into one of two groups: general-purpose and cryptographic. We learned the traits of a good hash function and how to test for those traits. And we got to survey a handful of general-purpose functions.
Now we shift our focus to those functions that make up the cryptographic group. First, we learn what a function needs to belong to that group. Then we explore a handful of uses for cryptographic hash functions. Next, we study three types of hash functions, divided in terms of origins. We learn how each function behaves and how each one measures up against an avalanche test.
When Hashes Get Secure
Cryptographic hash functions share traits that are unique amongst hash algorithms. First, their input is often, if not always, in the form of a byte stream. Hash output is a byte stream of fixed length, but some functions are able to emit variable-length hashes. Cryptographic hash functions run
slower than their general-purpose cousins. On the other hand, they are less likely to suffer from collisions.Uses for cryptographic hashes
Because of their greater resistance to collisions, cryptographic hash functions play an important role in many security applications. One popular use is in
validating critical data.
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