- Hash Function Examples
Hash functions take an input, in this case a device’s MAC address, and produce a random series of letters and numbers as the output, the hash value. Attackers should not be able to take the hash. MAC spoofing you might want to consider concatenating the hash with a random salt before generating the hash. MD5 will serve the purpose of a producing a unique hash but if your application requires countermeasures to dictionary attacks, using tools such as Hashcat and John the Ripper- for finding plaintext MAC adresses from hashes- consider. Difference between a Mac and a Hash function. Hash functions are used in practice as a form of authentication. For example, when downloading a file, one can check for errors by computing the hash of the file (e.g. Using SHA-2) and checking whether the output of the hash matches a pre-computed value that was published on the download page.
Cryptographic Hash Functions
A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size (a hash function) which is designed to also be one-way function, that is, a function which is infeasible to invert.
The input data is often called the 'message', and the output (the hash value or 'hash') is often called the 'message digest' or simply the 'digest'.
Download QuickHash hash checker for Windows, Mac, and Linux (Debian) from quickhash-gui.org. Hash Generator (Windows) Hash Generator is another free hash checker tool that can generate and compute the checksums or hashes of no less than 16 popular hash algorithm types that include: MD5 family (md2, md4, md5) SHA family (sha1, sha256, sha384.
Cryptographic hash functions have many information-security applications, notably in digital signatures, message authentication codes (MACs), and other forms of authentication. They can also be used as ordinary hash functions, to index data in hash tables, for fingerprinting, to detect duplicate data or uniquely identify files, and as checksums to detect accidental data corruption.
An example application of a hash function is password verification. Storing all user passwords as cleartext can result in a massive security breach if the password file is compromised. One way to reduce this danger is to only store the hash digest of each password. To authenticate a user, the password presented by the user is hashed and compared with the stored hash (note that this approach prevents the original passwords from being retrieved if forgotten or lost, and they have to be replaced with new ones). The password is often concatenated with a random, non-secret salt value before the hash function is applied. The salt is stored with the password hash. Because users have different salts, it is not feasible to store tables of precomputed hash values for common passwords.
Hash Function Examples
MD5
Shasum
Note: the flag
-a
default algorithm is 1
(i.e. SHA1)Instead of piping a string you can run
But you'll need to add a carriage return/line break and then.
Execute
shasum
and type stringBut you'll need to add a carriage return/line break and then.
Execute
<ctrl-d>
(which registers an EOF on standard input)OpenSSL
Note: use
-hmac 'some-key'
to convert algorithm into a HMACEncryption
Encryption transforms data from a cleartext to ciphertext and back (given the right keys), and the two texts should roughly correspond to each other in size: big cleartext yields big ciphertext, and so on. 'Encryption' is a two-way operation.
Hashes, on the other hand, compile a stream of data into a small digest (a summarized form: think 'Reader's Digest'), and it's strictly a one way operation.
The Advanced Encryption Standard (AES) is a family of ciphers with different key and block sizes. The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data. Photo slideshow on mac.
The downside of symmetrical encryption is the key needs to be transported somehow without being compromised. This is the problem asymmetric encryption solves and is primarily used with online communication (SSL/TLS).
Salt
![Hash Hash](/uploads/1/3/4/0/134070211/542739615.jpg)
A salt is a random, non-secret value which is combined with a password before a hash function is applied.
Salts help combat the use of rainbow tables for cracking passwords. A rainbow table is a large list of pre-computed hashes for commonly used passwords. For a password file without salts, an attacker can go through each entry and look up the hashed password in the rainbow table. If the look-up is considerably faster than the hash function (which it often is), this will considerably speed up cracking the file. However, if the password file is salted, then the rainbow table would have to contain 'salt . password' pre-hashed. If the salt is long enough and sufficiently random, this is very unlikely.
MAC
A Message Authentication Code (MAC) is a string of bits that is sent alongside a message. The MAC depends on the message itself and a secret key. No one should be able to compute a MAC without knowing the key. This allows two people who share a secret key to send messages to each without fear that someone else will tamper with the messages.
HMAC
HMAC is a recipe for turning hash functions (such as MD5 or SHA256) into MACs. So HMAC-MD5 and HMAC-SHA256 are specific MAC algorithms, just like QuickSort is a specific sorting algorithm.
Checksum
A checksum has a special purpose --- it verifies or checks the integrity of data. 'Good' checksums are easy to compute, and can detect many types of data corruptions (e.g. one, two, three erroneous bits).
Openoffice download mac 10.4. A checksum for a string should include each and every bit, and order matters. This means that 'aaaaaaaaaaba' would hash the same as 'aaaaaaaaaaab' where as a checksum could identify the difference.
Hash Collisions
A hash 'collision' occurs when two different data inputs generate the same resulting hash. The likelihood of this happening depends on which function you use.
For example:
md5
generates 128-bit hashessha1
generates 160-bit hashessha2
generates 224, 256, 384, or 512 bit hashes
Note: CIDR blocks are constructed from bits as well
- Cryptography Tutorial
- Cryptography Useful Resources
- Selected Reading
Hash Function App Mac Os
In the last chapter, we discussed the data integrity threats and the use of hashing technique to detect if any modification attacks have taken place on the data.
Another type of threat that exist for data is the lack of message authentication. In this threat, the user is not sure about the originator of the message. Message authentication can be provided using the cryptographic techniques that use secret keys as done in case of encryption.
![Hash Hash](/uploads/1/3/4/0/134070211/498668812.png)
Message Authentication Code (MAC)
MAC algorithm is a symmetric key cryptographic technique to provide message authentication. For establishing MAC process, the sender and receiver share a symmetric key K.
Essentially, a MAC is an encrypted checksum generated on the underlying message that is sent along with a message to ensure message authentication.
Carcassonne board game expansions. The process of using MAC for authentication is depicted in the following illustration − How to get rid of booking app on mac.
Let us now try to understand the entire process in detail −
Hash Mac Address
- The sender uses some publicly known MAC algorithm, inputs the message and the secret key K and produces a MAC value.
- Similar to hash, MAC function also compresses an arbitrary long input into a fixed length output. The major difference between hash and MAC is that MAC uses secret key during the compression.
- The sender forwards the message along with the MAC. Here, we assume that the message is sent in the clear, as we are concerned of providing message origin authentication, not confidentiality. If confidentiality is required then the message needs encryption. Kkmoon kxl-805 formaldehyde user manual.
- On receipt of the message and the MAC, the receiver feeds the received message and the shared secret key K into the MAC algorithm and re-computes the MAC value.
- The receiver now checks equality of freshly computed MAC with the MAC received from the sender. If they match, then the receiver accepts the message and assures himself that the message has been sent by the intended sender.
- If the computed MAC does not match the MAC sent by the sender, the receiver cannot determine whether it is the message that has been altered or it is the origin that has been falsified. As a bottom-line, a receiver safely assumes that the message is not the genuine.
Limitations of MAC
Mac Hash Tool
There are two major limitations of MAC, both due to its symmetric nature of operation −
- Establishment of Shared Secret.
- It can provide message authentication among pre-decided legitimate users who have shared key.
- This requires establishment of shared secret prior to use of MAC.
- Inability to Provide Non-Repudiation
- Non-repudiation is the assurance that a message originator cannot deny any previously sent messages and commitments or actions.
- MAC technique does not provide a non-repudiation service. If the sender and receiver get involved in a dispute over message origination, MACs cannot provide a proof that a message was indeed sent by the sender.
- Though no third party can compute the MAC, still sender could deny having sent the message and claim that the receiver forged it, as it is impossible to determine which of the two parties computed the MAC. Using a password reset disk for mac os x 10.13.
Mac Hash Key
Both these limitations can be overcome by using the public key based digital signatures discussed in following section.