The weak collision resistance property is sometimes also referred to as second preimage resistance: Given an arbitrary x there exists no x’ with x’ != x so that h(x) = h(x’) Strong collision resistance on the other hand is defined as: There exist no x and x’ with x != x’ so that h(x) = … Read more
Chen, I think your answer is correct. Some further background that might be helpful: In JavaScript, which was the original context for JSON, an object is like a hash map of strings to values, where some values are data, others are functions. You can think of each name-value pair as a property. But JavaScript doesn’t … Read more
Hash[original_hash.to_a.sample(n)] For Ruby 2.1, original_hash.to_a.sample(n).to_h
Assuming you have a Hash which maps old keys to new keys, you could do something like hsh.transform_keys(&key_map.method(:[]))
This question cannot be answered, in general, I fear. The issue is that there are many types of hash tables and balanced binary trees, and their performances vary widely. So, the naive answer is: it depends on the functionality you need. Use a hash table if you do not need ordering and a balanced binary … Read more
Inspired from this post and that post, I use this code to generate and verify hashed salted passwords. It only uses JDK provided classes, no external dependency. The process is: you create a salt with getNextSalt you ask the user his password and use the hash method to generate a salted and hashed password. The … Read more
If I understood correctly you want to return the %x format: you can import “encoding/hex” and use the EncodeToString method str := hex.EncodeToString(h.Sum(nil)) or just Sprintf the value: func md(str string) string { h := md5.New() io.WriteString(h, str) return fmt.Sprintf(“%x”, h.Sum(nil)) } note that Sprintf is slower because it needs to parse the format string … Read more
Switching to SHA512 will hardly make your website more secure. You should not write your own password hashing function. Instead, use an existing implementation. SHA256 and SHA512 are message digests, they were never meant to be password-hashing (or key-derivation) functions. (Although a message digest could be used a building block for a KDF, such as … Read more
I worked with Paul Larson of Microsoft Research on some hashtable implementations. He investigated a number of string hashing functions on a variety of datasets and found that a simple multiply by 101 and add loop worked surprisingly well. unsigned int hash( const char* s, unsigned int seed = 0) { unsigned int hash = … Read more