Note: m4 is being used so "_" prefixed strings are expanded (m4 is a macro pre-processor similar to the c preprocessor). My Type: CREATE TYPE UrlPair AS ( HostName varchar( _LIMIT_HOSTNAME ), ScriptName varchar( _LIMIT_SCRIPTNAME ) ...
I read that SHA-1 is being retired from the FIPS 180-2 standard. Apparently there are weaknesses in SHA-1 that led to this decision. Can anyone elaborate on the basis for that decision? Are there implications for the use of SHA-1 in commercial applications? My real questions are: What is the state of SHA-2 support in various cl...
I have a potential client that set up their website and membership system in ASP.NET 3.5. When their developer set up the system, it seems he turned off the security/hashing aspect of password storage and everything is stored in the clear. Is there a process to reinstall/change the secure password storage of ASP.NET membership without c...
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 enough to ...
Given that there are quite a few bioinformaticians around these days, wondering if any of you have seen examples of hash functions (or mapping mechanisms) occuring in nature? And if so how do they work? ...
Hi, I want to create a unique hash (16 chars long) of an arbitrary length String. Is there a good library that implements MD5 or SHA-1 for C++ with which I can achieve this? (and possibly an example of how to use it) ...
I am taking over a system that a previous developer wrote. The system has an administrator approve a user account and when they do that the system uses the following method to hash a password and save it to the database. It sends the unhashed password to the user. When the user logs in the system uses the exact same method to hash wha...
Given two different strings S1 and S2 (S1 != S2) is it possible that: SHA1(S1) == SHA1(S2) is True? If yes - with what probability? If not - why not? Is there a upper bound on the length of a input string, for which probably of getting duplicates is 0? OR is the calculation of SHA1 (hence probability of duplicates) independent o...
I want to generate a hash code for a file. Using C# I would do something like this then store the value in a database. byte[] b = File.ReadAllBytes(@"C:\image.jpg"); string hash = ComputeHash(b); Now, if i use say a Java program that implements the same hashing alogorithm (Md5), can i expect the hash values to be the equal to the val...
Hi fellas, A) Are there any FOSS programs out there that can manage to hashchange all files in a directory tree? B) Failing that, what methods could be used to develop this capability in a (crappy) self-written program without requiring the program to be sophisticated and content-aware? C) [Answered] Is there any (roughly) univers...
I am reading up the code of the HashMap class provided by the java 1.6 API and unable to fully understand the need of the following operation (found in the body of put and get methods) : int hash = hash(key.hashCode()); where the method hash() has the following body: private static int hash(int h) { h ^= (h >>> 20) ^ (h >>>...
I'm using a website as a frontend and all users are authenticated with the standard ASP.NET Membership-Provider. Passwords are saved "hashed" within a SQL-Database. Now I want to write a desktop-client with administrative functions. Among other things there should be a method to reset a users password. I can access the database with the...
Given the known weaknesses of MD5 and the recent (May 2009) weaknesses discussed in SHA1, how should new programs be salting & hashing their passwords? I've seen SHA-256 and SHA-512 suggested. Programming predominately in Ruby on Rails and using PostgreSQL -- but other languages and environments might also have to calculate password ha...
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 generating the digest quic...
I have a RESTful API containing a URI of /UserService/Register. /UserService/Register takes an XML request such as: <UserRegistrationRequest> <Password>password</Password> <Profile> <User> <UserName>username</UserName> </User> </Profile> </UserRegistrationRequest> I have the following questions given the above sce...
I'm on a personal quest to learn how the rsync algorithm works. After some reading and thinking, I've come up with a situation where I think the algorithm fails. I'm trying to figure out how this is resolved in an actual implementation. Consider this example, where A is the receiver and B is the sender. A = abcde1234512345fghij B = abc...
I am using the djb2 algorithm to generate the hash key for a string which is as follows hash(unsigned char *str) { unsigned long hash = 5381; int c; while (c = *str++) hash = ((hash << 5) + hash) + c; /* hash * 33 + c */ return hash; } Now with every loop there is a multiplication with two big numbers, After ...
Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few ...
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. ...
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) collisions. So, here is what I am doing...