Does the MD5 algorithm always generate the same output for the same string?
Yes, otherwise MD5 would be useless for things like file verification. What reason would you have for non deterministic output?
hash
Rspec match array of hashes
how about? hashes = [{“foo” => “1”, “bar” => “2”}, {“foo” => “2”, “bar” => “2”}] expect(hashes).to include(include(‘foo’ => ‘2’))
Why does double splat only work with symbol keys?
I ran into something like this recently. If you’re in Rails and you have a method that takes keyword arguments and you have a strong params hash that you want to send to it, you can use symbolize_keys on the params hash and it will properly separate out the arguments, no double splat needed. Model … Read more
Detecting if two images are visually identical
findimagedupes is pretty good. You can run “findimagedupes -v fingerprint images” to let it print “perceptive hash”, for example.
Shortening/Rehashing UUIDs
1) To shorten the UUID, you can simply XOR the top half with the bottom (and repeat until it’s short enough for you). This will preserve the distribution characteristics. Like any solution that shortens the output, it will increase the possibility of collision due to the birthday paradox 2) XOR amounts to a trivial hash, … Read more
A fast hash function for string in C#
static UInt64 CalculateHash(string read) { UInt64 hashedValue = 3074457345618258791ul; for(int i=0; i<read.Length; i++) { hashedValue += read[i]; hashedValue *= 3074457345618258799ul; } return hashedValue; } This is a Knuth hash. You can also use Jenkins.
What is the difference between Obfuscation, Hashing, and Encryption?
Hashing is a technique of creating semi-unique keys based on larger pieces of data. In a given hash you will eventually have “collisions” (e.g. two different pieces of data calculating to the same hash value) and when you do, you typically create a larger hash key size. obfuscation generally involves trying to remove helpful clues … Read more
Do I need a “random salt” once per password or only once per database?
A new salt should be randomly generated for each user and each time they change their password as a minimum. Don’t just rely on a site wide salt for example, as that defeats the point of using a salt in the first place. Using a unique salt for each user is so that if two … Read more
Python check that key is defined in dictionary [duplicate]
Use the in operator: if b in a: Demo: >>> a = {‘foo’: 1, ‘bar’: 2} >>> ‘foo’ in a True >>> ‘spam’ in a False You really want to start reading the Python tutorial, the section on dictionaries covers this very subject.