A user created one hash value from a block of data. if they hash the data the same way later and get a different value, what does this indicate?

A hash is a one-way digest function. It takes a number of input bytes and computes a fixed-length value from it. If you compute the same hash again, you get the same result. Generally the numeric value of the length of the input is not considered, as the data is inherently changed if you change the length. Hashes cannot be decrypted. They are lossy compression functions by nature and in most cases you cannot recover the full original data from them (this may not be the case for non-cryptographic indexing hash functions and small input values). There are three main types of hash function: those used for indexing, integrity, and cryptography. An indexing hash (e.g. MurmurHash or Java's hashCode) can be used to divide equal or very similar values into groups for improved performance in collection operations. For example, by precomputing a hash of each object and keeping the internal array for a collection sorted by the objects' hashes, lookups can be performed in worst case O(log n) time rather than O(n) using a • Extremely high performance • Generally specialised to certain input data types (e.g. ASCII strings or pointers) • In some cases, designed to produce output values which represent the magnitude of the input value. For example, in string searching, you might choose to convert the first four characters to their ASCII integer values and interpret those together as a 32-bit integer, since sorting that integer also pre-sorts the list alphabetically. An integrity hash (e.g...

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 the value is stored, but that's where my knowledge stops. Could anyone clarify the process? Edit: I'm not asking specifically about how hash codes are calculated, but a general overview of how a hash table works. Here's an explanation in layman's terms. Let's assume you want to fill up a library with books and not just stuff them in there, but you want to be able to easily find them again when you need them. So, you decide that if the person that wants to read a book knows the title of the book and the exact title to boot, then that's all it should take. With the title, the person, with the aid of the librarian, should be able to find the book easily and quickly. So, how can you do that? Well, obviously you can keep some kind of list of where you put each book, but then you have the same problem as searching the library, you need to search the list. Granted, the list would be smaller and easier to search, but still you don't want to search sequentially from one end of the library (or list) to the other. You want something that, with the title of the book, can give you the right spot at once, so all you have to do is just stroll over to the right shelf, and pick up the book. But how can that be done...

One concept that you will meet time and time again in any discussion of cybersecurity is the concept of a hash. These long strings of apparently random numbers and letters are generated and used in several important ways. Some What is a Hashing Algorithm? Hashes are the output of a hashing algorithm like MD5 (Message Digest 5) or SHA (Secure Hash Algorithm). These algorithms essentially aim to produce a unique, fixed-length string – the hash value, or “message digest”– for any given piece of data or “message”. As every file on a computer is, ultimately, just data that can be represented in binary form, a hashing algorithm can take that data and run a complex calculation on it and output a fixed-length string as the result of the calculation. The result is the file’s hash value or message digest. To calculate a file’s hash in Windows 10, use PowerShell’s built in Get-FileHash cmdlet and feed it the path to a file whose hash value you want to produce. By default, it will use the SHA-2 256 algorithm: You can change to another algorithm by specifying it after the filepath with the -Algorithm switch. Passing the result to Format-List also gives a more reader-friendly output: For Mac and Linux users, the command line tools shasum and md5 serve the same purpose. As we’ll see in a moment, regardless of whether you’re using Windows, Mac or Linux, the hash value will be identical for any given file and hashing algorithm. How Hashes Establish Identity Hashes cannot be reversed, so si...

According to my understanding, Hashing is a process of producing a unique fixed length (let's assume 64bit) output to an input of ANY length. (correct me if am wrong) So if I take all the (x) possible 64bit hash values that a hash function can produce and append a 0 or 1 at the end of it. I get a list of size 2x (where each hash is 65bit long). If I give all the 2x combinations as the input to the same hash function, how can it generate a unique hash for all the inputs? You are correct. This is called a hash collision, and it's a real thing. The reason it's not a bigger deal is that the number of hashes is so overwhelmingly large that these types of collisions are rare. Your example of 64 bits is a little unrealistic, though. 256 bits or 512 bits is a more likely scenario. (Even 128 is no longer considered strong enough.) And the range of hashes in this case is so large that finding inputs that create a hash collision is very difficult. By the m1 != m2 such that their hash are equal H(m1) = H(m2) Therefore, one cannot generate unique hashes for the inputs. With a very very small probability ( negligible ), there will be a collision. Even, inside of 2 64 possible values, there can be a collision for a hash function with 64-bit output. Better use a Hash function like • SHA3 family can generate 224, 256, 384, or 512-bit outputs.

Short answer: Yes, except the lower/uppercase may vary. Hashes are (usually) hexadecimal anyway, so they can be treated as case-insensitive. Of course when outputted in another format (like the raw binary data, e.g. 128 'random' bits for MD5), it may be case sensitive. The output will always be the same though. Hash functions are However, note that hash functions take sequences of bits as input. When we "hash a string", we actually convert a sequence of characters into a sequence of bits, and then hash it. There begins the trouble. Consider the string "café": among all the possible conversions to bits, all of the following are common: 63 61 66 e9 ISO-8859-1 ("latin-1") 63 61 66 ca a9 UTF-8 63 61 66 65 cc 81 UTF-8 (NFD) ef bb bf 63 61 66 ca a9 UTF-8 (with BOM) ef bb bf 63 61 66 65 cc 81 UTF-8 (NFD with BOM) 63 00 61 00 66 00 e9 00 UTF-16 little-endian 00 63 00 61 00 66 00 e9 UTF-16 big-endian ff fe 63 00 61 00 66 00 e9 00 UTF-16 little-endian (with BOM) fe ff 00 63 00 61 00 66 00 e9 UTF-16 big-endian (with BOM) 63 00 61 00 66 00 65 00 01 03 UTF-16 little-endian (NFD) 00 63 00 61 00 66 00 65 03 01 UTF-16 big-endian (NFD) ff fe 63 00 61 00 66 00 65 00 01 03 UTF-16 little-endian (NFD with BOM) fe ff 00 63 00 61 00 66 00 65 03 01 UTF-16 big-endian (NFD with BOM) and all will yield very different hash values when processed with a given hash function. You have to be very precise about what you do when dealing with cryptographic functions; every bit counts. @OskarSkog you are wron...

Loading... You use hashing on a daily basis while surfing online but may not know it! Let’s explore how a cryptographic hash works in layman’s terms Cryptography includes all the tools and techniques that help to protect the data in transit and at rest. A hash function in cryptography is one of the big players, yet many people don’t know what it is or what it does. Frankly, hashing is everywhere. For example, do you know your passwords are frequently stored on prominent websites with hashing? In fact, the fingerprint locks on our phones and laptops also utilize hashing technology! So, let’s explore what a hash function in cryptography is and why it’s important. We’ll cover how hashing works, what a cryptographic hash function does (and doesn’t do), and how to make hashing more secure in terms of password storage. Download: Certificate Management Checklist Essential 14 Point Free PDF What Is Hashing? The Definition of a Hash Function in Cryptography If you buy a new phone and its shrink wrap is torn off or damaged, you can immediately tell that someone has opened, used, replaced, or damaged the phone. A cryptographic hash in encryption is much the same but for data instead of a physical object. In the same way, hashing is like putting virtual shrink wrap on a piece of software, application, or data to inform users if it has been modified in any way. But what is hashing? Hashing, or a In a more technical sense, it’s a technique that uses a mathematical operation to shrink a ...

I have 2 excel documents and I want to check if they are exactly the same, apart from the file name. For example, the files are called fileone.xls and filetwo.xls. Apart from the file names, their contents are presumed to be identical but this is what i want to check. I've been looking for ways to review this and without installing a bunch of plugins. There doesn't seem a straight forward way. I've tried generating MD5 hashes for both files. When the hashes are identical, does this mean that the file contents are 1:1 the same? When the hashes are identical, does this mean that the file contents are 1:1 the same? All files are a collection of bytes (values 0-255). If two files MD5 hashes match, both those collections of bytes are extremely likely the exact same (same order, same values). There's a very small chance that two files can generate the same MD5, which is a 128 bit hash. The probability is: Probability of just two hashes accidentally colliding is 1/2 128 which is 1 in 340 undecillion 282 decillion 366 nonillion 920 octillion 938 septillion 463 sextillion 463 quintillion 374 quadrillion 607 trillion 431 billion 768 million 211 thousand 456. (from an answer on Hashes are meant to work in "one direction only" - i.e. you take a collection of bytes and get a hash, but you can't take a hash and get back a collection of bytes. Cryptography depends on this (it's one way two things can be compared without knowing what those things are.) Around the year 2005, methods were d...