undefined method `[]’ for nil:NilClass says you tried to do something[index] but something is nil. Ruby won’t let you use nil as an array (ie. call the [] method on it). The problem is not on the attributs.each line but on the line following which calls the [] method on attribut. This indicates something in … Read more
First, it usually does not matter that much in practice. Most hash functions are “good enough”. But if you really care, you should know that it is a research subject by itself. There are thousand of papers about that. You can still get a PhD today by studying & designing hashing algorithms. Your second hash … Read more
I went through many articles related to this topic, such as this: Using PHP 5.5’s password_hash and password_verify function Yet, I’m unsure if I’m hashing and salting the correct way or over doing it! I want to use my own salt and then hash. Both salt and hashed password stored in the database in two … Read more
I’m looking for an explanation of how a hash table works – in plain English for a simpleton like me! For example, I know it takes the key, calculates the hash (I am looking for an explanation how) and then performs some kind of modulo to work out where it lies in the array where … Read more
First you shoud maybe read this article. When you use lists and you are looking for a special item you normally have to iterate over the complete list. This is very expensive when you have large lists.A hashtable can be a lot faster, under best circumstances you will get the item you are looking for with … Read more
So I finally figured it out. The “infohash” is the SHA1 Hash over the part of a torrent file that includes: ITEM: length(size) and path (path with filename) Name: The name to search for Piece length: The length(size) of a single piece Pieces: SHA1 Hash of EVERY piece of this torrent Private: flag for restricted … Read more
Java’s Set and Map interfaces specify two very different collection types. A Set is just what it sounds like: a collection of distinct (non-equal) objects, with no other structure. A Map is, conceptually, also just what it sounds like: a mapping from a set of objects (the distinct keys) to a collection of objects (the values). Hashtable and HashMap both implement Map, HashSet implements Set, and they all use hash codes … Read more
From the error, I infer that referenceElement is a dictionary (see repro below). A dictionary cannot be hashed and therefore cannot be used as a key to another dictionary (or itself for that matter!). You probably meant either for element in referenceElement.keys() or for element in json[‘referenceElement’].keys(). With more context on what types json and referenceElement are and what they contain, we will be … Read more
A hash is an fixed sized integer that identifies a particular value. Each value needs to have its own hash, so for the same value you will get the same hash even if it’s not the same object. Hash values need to be created in such a way that the resulting values are evenly distributed … Read more
SHA-256 is a cryptographic (one-way) hash function, so there is no direct way to decode it. The entire purpose of a cryptographic hash function is that you can’t undo it. One thing you can do is a brute-force strategy, where you guess what was hashed, then hash it with the same function and see if … Read more