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Search found 337 results on 14 pages for 'hashing'.

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  • Combining Java hashcodes into a "master" hashcode

    - by Nick Wiggill
    I have a vector class with hashCode() implemented. It wasn't written by me, but uses 2 prime numbers by which to multiply the 2 vector components before XORing them. Here it is: /*class Vector2f*/ ... public int hashCode() { return 997 * ((int)x) ^ 991 * ((int)y); //large primes! } ...As this is from an established Java

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  • HashSet vs. List performance

    - by Michael Damatov
    It's clear that a search performance of the generic HashSet<T> class is higher than of the generic List<T> class. Just compare the hash-based key with the linear approach in the List<T> class. However calculating a hash key may itself take some CPU cycles, so for a small amount of items the linear search can

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  • Computing MD5SUM of large files in C#

    - by spkhaira
    I am using following code to compute MD5SUM of a file - byte[] b = System.IO.File.ReadAllBytes(file); string sum = BitConverter.ToString(new MD5CryptoServiceProvider().ComputeHash(b)); This works fine normally, but if I encounter a large file (~1GB) - e.g. an iso image or a DVD VOB file - I get an Out of Memory exception.

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  • SHA-1 and Unicode

    - by Andrew
    Hi everyone, Is behavior of SHA-1 algorithm defined for Unicode strings? I do realize that SHA-1 itself does not care about the content of the string, however, it seems to me that in order to pass standard tests for SHA-1, the input string should be encoded with UTF-8.

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  • Tracking unique versions of files with hashes

    - by rwmnau
    I'm going to be tracking different versions of potentially millions of different files, and my intent is to hash them to determine I've already seen that particular version of the file. Currently, I'm only using MD5 (the product is still in development, so it's never dealt with millions of files yet), which is clearly not long

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  • Is SHA-1 secure for password storage?

    - by Tgr
    Some people throw around remarks like "SHA-1 is broken" a lot, so I'm trying to understand what exactly that means. Let's assume I have a database of SHA-1 password hashes, and an attacker whith a state of the art SHA-1 breaking algorithm and a botnet with 100,000 machines gets access to it. (Having control over 100k home

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  • Salt question - using a "random salt"

    - by barfoon
    Hey everyone, Further to my question here, I have another question regarding salts. When someone says "use a random salt" to pre/append to a password, does this mean: Creating a static a 1 time randomly generated string of characters, or Creating a string of characters that changes at random every time a password is

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  • Cache SHA1 digest result?

    - by johnathan
    I'm storing several versions of a file based on a digest of the original filename and its version, like this: $filename = sha1($original . ':' . $version); Would it be worth it to cache the digest ($filename) in memcache as a key/value pair (the key being the original + version and value the sha1 hash), or is

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  • Is it possible to get identical SHA1 hash?

    - by drozzy
    Given two different strings S1 and S2 (S1 != S2) is it possible that: SHA1(S1) == SHA1(S2) is True? If yes - with what probability? Is there a upper bound on the length of a string, for which probably of getting duplicates is 0? If not - why not? Thanks

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  • using Multi Probe LSH with LSHKIT

    - by Yijinsei
    Hi Guys, I have read through the source code for mplsh, but I still unsure on how to use the indexes generated by lshkit to speed up the process in comparing feature vector in Euclidean Distance. Do you guys have any experience regarding this?

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  • Cycles/byte calculations

    - by matskn
    Hi ! In Crypto communities it is common to measure algorithm performance in cycles/byte. My question is, which parameters in the CPU architecture are affecting this number? Except the clockspeed ofcourse :)

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  • Good hash function for a 2d index

    - by rlbond
    I have a struct called Point. Point is pretty simple: struct Point { Row row; Column column; // some other code for addition and subtraction of points is there too } Row and Column are basically glorified ints, but I got sick of accidentally transposing the input arguments to functions and gave

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  • How does a hash table work?

    - by Arec Barrwin
    I'm looking for an explanation of how a hashtable works - in plain English for a simpleton like me! For example I know it takes the key, calculates the hash (how?) and then performs some kind of modulo to work out where it lies in the array that the value is stored, but that's where my knowledge stops. Could

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  • MAD method compression function

    - by Jacques
    I ran across the question below in an old exam. My answers just feels a bit short and inadequate. Any extra ideas I can look into or reasons I have overlooked would be great. Thanx Consider the MAD method compression function, mapping an object with hash code i to element [(3i + 7)mod9027]mod6000 of the

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  • How do I find hash value of a 3D vector ?

    - by brainydexter
    I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any)

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  • checking crc32 of a file

    - by agent154
    This is not really a "how to" question. Is there a "standard" file structure that applications use to store the checksums of files in a folder? I'm developing a tool to check various things like crc32, md5, sha1, sha256, etc... I'd like to have my program store the various hashes in files in the

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  • Persisting hashlib state

    - by anthony
    I'd like to create a hashlib instance, update() it, then persist its state in some way. Later, I'd like to recreate the object using this state data, and continue to update() it. Finally, I'd like to get the hexdigest() o the total cumulative run of data. State persistence has to survive across

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  • How does the hash part in hash maps work?

    - by sub
    So there is this nice picture in the hash maps article on Wikipedia: Everything clear so far, except for the hash function in the middle. How can a function generate the right index from any string? Are the indexes integers in reality too? If yes, how can the function output 1 for John

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