Hash long string to short string. However, I'd like to propose an alternate approach.
Hash long string to short string hash(string2); The small prime is in there to avoid equal hash code for switched values, i. md5() seems to be kind of long (32-characters). An important part of the security of a hashing algorithm is the algorithms collision resistance. com The hash should not be longer than 8 characters. By truncating the hash, you're increasing the likelihood of a collision because only Oct 13, 2016 · First, as pointed out by @wildplasser, the hash requires that all bytes of both strings must be traversed in order to calculate the two hash values, whereas the simple compare is fast, and only needs to traverse bytes until the first difference is found, which may be much less than the full string length. Jun 6, 2009 · I am looking for a PHP function that creates a short hash out of a string or a file, similar to those URL-shortening websites like tinyurl. The original Git hash is 40 bytes long while short is only 8 bytes long. What are some alternative hash functions that perhaps use every letter in the alphabet as well as integers that are perhaps shorter in string length and have low collision rates? Thanks! Jul 15, 2011 · As a side-note: obviously your += into a Long only works for short strings. hashCode() is guaranteed to generate the same hash code for multiple strings. Mar 20, 2025 · It operates on 32-bit integers and converts the result to a base 36 string. We want to solve the problem of comparing strings efficiently. in Lisp. 23 % collision rate; SHA1. I came up with the following simple implementation: static short shortHashCode(String str) { int strHashCode = str. In general if you have a hashtable that maps aKey The String Converter - Hash, Encode and Decode strings using any known technique. So in many A hash is a one way scrambling and shortening of the data. While this may seem large, it's relatively small in the context of other hash functions, especially if you're looking to hash a larger number of strings. 4 bytes; Despite short outputs, the collision probability of natural language strings is generally small; Restoring / decoding the original string is accurate. Mar 24, 2009 · But this causes no problems when the goal is to compute a hash function. Is there any way to compress or make the string just a bit shorter? Notes: I am using the generated string to create a directory in the file system and I can't use the original URL because it contains slashes and other punctuation and I would like to keep the checks at a minimum. Multiple hashing algorithms are supported including MD5, SHA1, SHA2, CRC32 and many other algorithms. It's 32 Have you looked into comparing the data itself before calculating the strings? E. choice(string. e. I would like to get the shortest unambiguous SHA-1 hash string version of it. 29 billion unique values. The value returned by a hash function called hash digest, hash value, hash code, hash sum, checksum, or simply "hash. Nice. The photos have standardized ID tags of "Site Abbreviation" + "Timestamp". This mean that if I hash ThingToHash1 the result (hopefully) won't match the hash for any other input. But it doesn't go backwards. By applying the input difference on an MD5 input, you have a small but higher-than-random probability of finding the expected difference in the output. Another alternative would be to fold two characters at a time. the same hash for two different strings. Short strings are a really common case, and hashCode should handle that All these points don't necessarily conflict each other! In fact, I feel like a legitimate suggestion for improvement is an algorithm that is perfect for really short strings and still better than average for long strings by trading-off against "medium" string performance. May 7, 2013 · I have a regular long SHA-1 hash string. I would like to shorten that to 7-10 (or even shorter) characters long. Mar 8, 2021 · None of those hash functions were designed to have this property. Apr 2, 2020 · I want to hash an arbitrary long string (e. This means you can have both encode() and decode() functions. js module to generate short, alpha-number, undecryptable and unique hash id from a long string (utf8 format). hashCode(); short shorterHashCode = (short) (strHashCode % Short. I see your new comment about using the string in a URL. Try out the sfold hash function. Share Follow May 13, 2013 · There are many more than 2^32 possible strings, so String. No, actually the user asked how to generate a 6 character long hash string that can be used using JavaScript. Second, it needs to use HTTPS. Sep 8, 2012 · The hashing approaches already mentioned will work fine for creating unique short strings that will probably uniquely identify your URL's. Avoid creating duplicated short strings. So we need a Bijective Function . For example, using sha512: Jul 25, 2014 · MY_TABLE [ full_text: TEXT text_hash: varchar(255) - indexed ] Thing is, I cannot use String. Feb 16, 2012 · long has 64 bits. You can use hashtext if you want integer hash values, or hashtextextended if you prefer bigint hash values. hashCode() as: Implementation may vary across JVM versions. Jun 27, 2014 · I have a library of ~25,000 photographs, each in a (linked) container, 1 photo per record. Basically you have 16-bytes of data in the MD5 hash string. ) Jul 23, 2010 · This is for the purpose of having a nice short URL which refers to an md5 hash in a database. Aug 29, 2015 · string input = //Some input text that includes the datetime the hash was created; using (SHA1Managed sha1 = new SHA1Managed()) { var hash = sha1. Create a database table with two columns, ID (an integer) and URL (a string). Aug 23, 2017 · So you’d have something like “aM8k-SalesSouth-IvanIvanovicIvan” (-ov got truncated). Jan 3, 2025 · One important thing to note is, the long URL should also be uniquely identifiable from the short URL. [A-Z,a-z,0-9]. After a few initial passes of morphological normalization on the original words in the text, I throw away the string values and use hash codes instead. Then you can shorten that further by XORing sections of the digest with other sections. Category: Web Tools:: This tool is also available through the Codepunker API. However, it becomes difficult to manage it (in terms of using typing or displaying), and that's why the short version is used. A mini Node. " Feb 21, 2015 · MD5 would be better described as a flawed cryptographic hash function, rather than a "non-cryptographic hash function". hashCode(guid); For older versions of Java you can use the following: Long. js. We would choose "kangaroo" because it is easily pronounceable. hashCode(last half of string) Thats just 16 bytes of hashes and as the size of the string is fixed, would this give a unique 16byte hash for every different string? This is similar to using a bloom filter, but I need to ensure there are absolutely NO hash collisions. Bernstein's DJB2 performs especially bad on short strings. You'll notice there is no decode on an md5 object. Apr 29, 2021 · The process of hashing in cryptography is to map any string of any given length, to a string with a fixed length. N = hash(o,R) You can use this number to produce a short string as follows: Choose a range of characters (alphabeth) to choose from e. It will return the hash equivalent of a string. An integer has 32 bit positions and each position has two values. public static String hash_function(String bmpBytes) Aug 20, 2015 · Yes, shortening a hash does reduce the security of the hash. By taking the ASCII decimal value of each character, multiplying it by 10, and adding all of the values computed together for each character in a string. – Dec 26, 2018 · That sums to 2^n - 1 strings, so by the piegonhole principle, either two strings have the same compressed form (uh-oh — this is the same idea as a hash collision) — or some compressed form is longer than the original, which can happen easily in Huffman encoding when storing the map if your original string is short and made of a lot of . This means the total number of possible hash outputs is limited to 2^32, or about 4. Jul 4, 2024 · Last update: July 4, 2024 Translated From: e-maxx. Convert that hash to base64 instead of hex, giving us 64 possible values for each character. (The article gives many examples, such as !~ and "_. Edit: some great suggestions/solutions here - thanks! A mini js lib to generate short, alpha-number, undecryptable and unique hash id from a long string (utf8 format). hash(string1) * 31 + MyHash. Because it has much more collisions than similar functions (FNV, Jenkins OAAT and MurmurOAAT) while having comparable throughput. The random_choice is the fastest, has fewer collisions but is IMO slightly harder to read. Encode or decode strings to and from base64. from pigeon hole principle - you cannot get a unique hashing for 9 chars long strings to a long. ascii_uppercase + string. This post will discuss the key features, implementation, advantages and drawbacks of the Polynomial Rolling Hash Function. {'foo','bar'} and {'bar','foo'} aren't equal and should have a different hash code. See what happens for short strings, and also for long strings. ) A lot of the answers do not provide a random string consisting of characters 0-9, a-z, A-Z: Here is a working solution which will give you one of approx. An interned string is a string object whose value is the address of the actual string bytes. Feb 27, 2017 · I want to hash a string of length up-to 30. Convert digest to hex string. Mar 24, 2010 · I'd like to set non-integer primary keys for a table using some kind of hash function. Mar 4, 2015 · Since the checksum of the string with a newline appended is just as good a hash as the checksum of the string itself, there is no problem as long as you always use the same mechanism to produce the hash. Generating a Hash: Method 3 Using Hexadecimal Output. MAX_VALUE); return shorterHashCode; } The value returned by a hash function is often called a hash, message digest, hash value, or checksum. randomUUID is a function that generates a string containing 36 characters long UUID. equals() to compare keys while searching the selected hash chain. There are an infinity of strings with a given hash and beginning with a given substring. . var_dump (strlen (hash ('md5', 'string to check', true))); // int(16) PS: You can always use floating points to store a very big number but for "common humans" binary types by and large are easier to check, understand and maintain, so i recommend to use binary, but if you are about speed them floating point could be your friend. May 29, 2017 · I have a set of ASCII strings, let's say they are file paths. The most readable is shortuuid_random but is an external dependency and is slightly slower and has 6x the collisions. ToCharArray(). I want to find a fast hashing function that will read the long text value and produce a long hash value for it, say 64 symbols long. If I generate an short id randomly then I would have to check every time if that shortid is available. To create a hash, it must be passed into a hash function. Truncate the hash to the desired length. Again, what changes in the strings affect the placement, and which do not? Can you figure out how to pick strings that go to a particular slot in the table? Mar 23, 2012 · However, if you use a cryptographic hash you shorten the string to the length of hash. there is almost no point in using the popular DJB2 hash function for strings on Intel x86-64 (or AArch64 for that matter) architecture. A year later, we want to know the long string identifier of "kangaroo" - we just reverse-hash it, or we forward-hash all 87 long string identifiers created so far, and see which one converted to "kangaroo". URL) and a hash: string <=> hash Furthermore, we want this unique hash to be (much) shorter than the original string. Use a hash function to convert long string to short string. These are the following methods to Create Hash from String: Jul 17, 2014 · I have a 24 character long id which is guaranteed to be unique.
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