There’s a spatial hash function described in Optimized Spatial Hashing for Collision Detection of Deformable Objects. They use the hash function hash(x,y,z) = ( x p1 xor y p2 xor z p3) mod n where p1, p2, p3 are large prime numbers, in our case 73856093, 19349663, 83492791, respectively. The value n is the hash … 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
Basically it’s because the output of MD5 contains less information than the input. This is basically what distinguishes a hash algorithm from an encryption algorithm. Here’s a simple example: imagine an algorithm to compute the hash of a 10-digit number. The algorithm is “return the last 2 digits.” If I take the hash of 8023798734, … Read more
CRC32 works very well as a hash algorithm. The whole point of a CRC is to hash a stream of bytes with as few collisions as possible. That said, there are a few points to consider: CRC’s are not secure. For secure hashing you need a much more computationally expensive algorithm. Different CRC flavors exist … Read more
MD5 and SHA hashes in raw form are binary, however their common representation is a hex-encoded string, which contains characters [a-fA-F0-9]. So if this is what you meant, then characters G-Z, g-z are “excluded”. Another, less common, representation is Base64 encoding [0-9a-zA-Z+/].
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
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
There is technically a limit, but it’s quite large. The padding scheme used for SHA-256 requires that the size of the input (in bits) be expressed as a 64-bit number. Therefore, the maximum size is (264-1)/8 bytes ~= 2’091’752 terabytes. That renders the limit almost entirely theoretical, not practical. Most people don’t have the storage … Read more