Visit Our UNIX and Linux User Community

Hash Funtion properties

Thread Tools Search this Thread
Special Forums Cybersecurity Hash Funtion properties
# 1  
Old 05-02-2006
Hash Funtion properties

Here are some desirable properties for cryptographic hash functions:

These properties below are generally considered prerequisites:

* Preimage resistant: given h it should be hard to find any m such that h = hash(m).
* Second preimage resistant: given an input m1, it should be hard to find another input, m2 (not equal to m1) such that hash(m1) = hash(m2).
* Collision-resistant: it should be hard to find two different messages m1 and m2 such that hash(m1) = hash(m2).

For each of the following applications of hash functions, explain which of these three properties are needed and which are not.

(a) Cryptographic signatures are produced by computing a hash of a message, then applying a signature function to the hash of the message. Suppose Eve has a list of messages m1,, and their signatures computed using Bob's signing key, but does not have Bob's signing key. Assuming that the signature function is not susceptible to attack, it should not be possible for Eve to present Bob's signature on any message other than m1,

(b) Suppose that Eve works for a Certificate Authority. She does not have access to the special harware that computes digital signatures, but she knows the hash function. In addition, Eve can get messages signed, but every message that is signed automatically goes into a log file that Eve cannot change. Eve should not be able to produce a certificate signed by the Certificate Authority that does not appear in the log file.

Anybody can explain these to me?

# 2  
Old 05-02-2006

This is an easy problem elementary to any cryptography courses. Didn't your teacher cover it? However, please be reminded of the following forum rule here:

(6) Do not post classroom or homework problems.
Go and revise your textbook.

Previous Thread | Next Thread
Test Your Knowledge in Computers #385
Difficulty: Easy
The Linux uptime command show how long the hard drive has been powered down.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Need to print hash of hash in table format

Hi, I have a hash of hash where it has name, activities and count i have data like this - $result->{$name}->{$activities} = $value; content of that are - name - robert tom cat peter activities - running, eating, sleeping , drinking, work i need to print output as below ... (3 Replies)
Discussion started by: asak
3 Replies

2. Shell Programming and Scripting

Dynamically parse BibTeX and create hash of hash

Hello gurus, Iam trying to parse following BibTex file (bibliography.bib): @book{Lee2000a, abstract = {Abstract goes here}, author = {Lee, Wenke and Stolfo, Salvatore J}, title = {{Data mining approaches for intrusion detection}}, year = {2000} } @article{Forrest1996, abstract =... (0 Replies)
Discussion started by: wakatana
0 Replies

3. Shell Programming and Scripting

Compare values of hashes of hash for n number of hash in perl without sorting.

Hi, I have an hashes of hash, where hash is dynamic, it can be n number of hash. i need to compare data_count values of all . my %result ( $abc => { 'data_count' => '10', 'ID' => 'ABC122', } $def => { 'data_count' => '20', 'ID' => 'defASe', ... (1 Reply)
Discussion started by: asak
1 Replies

4. Shell Programming and Scripting

how to check/display/edit funtion

Hi, I have this output: $ type msq msq is a function I thought it an alias, can you tell me how to I can find this function and where ? Thanks for help. I'm on RH and HP-UX Best T Continued here (0 Replies)
Discussion started by: trento17
0 Replies

5. Shell Programming and Scripting

perl hash - using a range as a hash key.

Hi, In Perl, is it possible to use a range of numbers with '..' as a key in a hash? Something in like: %hash = ( '768..1536' => '1G', '1537..2560' => '2G' ); That is, the range operation is evaluated, and all members of the range are... (3 Replies)
Discussion started by: dsw
3 Replies

6. Shell Programming and Scripting

Perl Hash:Can not keep hash data in the same order that it was inserted

Can Someone explain me why even using Tie::IxHash I can not get the output data in the same order that it was inserted? See code below. #!/usr/bin/perl use warnings; use Tie::IxHash; use strict; tie (my %programs, "Tie::IxHash"); while (my $line = <DATA>) { chomp $line; my(... (1 Reply)
Discussion started by: jgfcoimbra
1 Replies

7. Shell Programming and Scripting

Assigning a hash to another hash key

Hello, I have a hash in hsh. I need to assign it to another hash globalHsh. I think the below statement does not work $globalHsh{$id} = %hsh; What is the right way to assign it? Thanks (3 Replies)
Discussion started by: rsanjay
3 Replies

8. Shell Programming and Scripting

Print Entire hash list (hash of hashes)

I have a script with dynamic hash of hashes , and I want to print the entire hash (with all other hashes). Itried to do it recursively by checking if the current key is a hash and if yes call the current function again with refference to the sub hash. Most of the printing seems to be OK but in... (1 Reply)
Discussion started by: Alalush
1 Replies

9. Programming

compile funtion

Hi, This is the first time, i am doing UNIX & C stuff. I have written one funtion like #include <stdio.h> seq(num) int num; { int i,sum; for (i=1; i<=num;i++) sum+=i; return(sum); } this seq funtion should have return values to unix script. like .. (4 Replies)
Discussion started by: sundarm
4 Replies

10. Post Here to Contact Site Administrators and Moderators

Delete funtion

Neo, eariler today i had tossed up a post then realized i didnt want it up so i tried to delete it and it wouldnt let me. is this a functionality that you have active? To allow a user to delete any topic they started would be a great thing, i think it will also help on not haveing double posts... (2 Replies)
Discussion started by: Optimus_P
2 Replies

Featured Tech Videos