What is Hashing?
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Hashing is the process of converting a given sequence of characters (string) into a fixed-length numeric value or key. A hash function is any function that can be used to map data of arbitrary size to a data of fixed size. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes.
Hash functions are used in many areas of computer science, but perhaps the most well-known use is in cryptography. Cryptographic hash functions are used in digital signatures, message authentication codes (MACs), and other forms of authentication. They are also used in many non-cryptographic applications, such as hash tables, and can be used to build data structures such as bloom filters.
What are some algorithms used in Hashing?
There are many different algorithms that can be used for hashing, but some of the most popular include MD5, SHA, RIPEMD-160, and Whirlpool. Each algorithm has its own strengths and weaknesses, so it’s important to choose one that is well-suited for the task at hand.
MD5 is a widely used hash function that produces a 128-bit hash value. It is typically used in conjunction with a secret key to create a message authentication code (MAC).
SHA is another widely used hash function that produces a 160-bit hash value. It is also typically used in conjunction with a secret key to create a MAC.
RIPEMD-160 is a less commonly used hash function that produces a 160-bit hash value. It is not as widely used as MD5 or SHA, but it may be more appropriate for some applications.
Whirlpool is a less commonly used hash function that produces a 512-bit hash value. Like RIPEMD-160, it is not as widely used as MD5 or SHA, but it may be more appropriate for some applications.
When choosing a hash function, it is important to consider the security requirements of the application. For example, if cryptographic security is required, then a strong hash function such as SHA should be used. On the other hand, if security is not as important, then a weaker hash function such as MD5 may be sufficient.
No matter which hash function is used, it is important to remember that no hash function is perfect. All hash functions are susceptible to collision attacks, meaning that it is possible to find two different inputs that produce the same output. However, some hash functions are more resistant to collision attacks than others. As a result, it is important to choose a hash function that is appropriate for the security requirements of the application.
Where is Hashing used?
Digital signatures are a type of cryptographic security that is often used to protect electronic documents. A digital signature uses a hashing algorithm to create a unique signature for a document. This signature can then be verified by anyone who has the original document and the corresponding public key.
Message authentication codes (MACs) are another type of cryptographic security that is used to protect messages. A MAC uses a hashing algorithm to create a unique code for a message. This code can then be verified by anyone who has the original message and the corresponding secret key.
Hash functions are also used in hash tables, which are data structures that are used to store data in a way that is efficient and easy to search. Hash tables use a function to map each piece of data to a unique index, making it quick and easy to find the data when it is needed.
Bloom filters are another type of data structure that uses hash functions. Bloom filters are used to store information about whether or not an element is present in a set. They are often used when it is not possible or practical to store the entire set of data.
Hash functions are also used in many other applications, such as password storage, file management, and checksums. They are a versatile tool that can be used in many different ways to solve a variety of problems.
Password storage is one area where hashing is often used. When a user creates a new account, they choose a password that will be used to login to their account. This password is then hashed and stored in the database. When the user tries to login, their password is hashed and compared to the hash that is stored in the database. If the two hashes match, then the user is granted access to their account.
File management is another area where hashing is often used. When a file is created, it is given a unique identifier that is known as a checksum. This checksum is used to ensure that the file has not been modified in any way. If the file is modified, then the checksum will no longer match and the file will be considered invalid.
Checksums are also used to verify the integrity of data. A checksum is a value that is computed from a piece of data. This value can then be used to verify that the data has not been changed in any way. For example, when downloading a file from the internet, the file may come with a checksum. This checksum can be used to make sure that the file has not been tampered with and is exactly the same as the original.
References
Hans Peter Luhn and the Birth of the Hashing Algorithm. (January 2018). IEEE Spectrum.
Cryptographic Module Validation Program. National Institute of Standards and Technology.
Hashing Algorithms. IBM Knowledge Center.
SHA-256 Hash Generator. Dan’s Tools.
MD5 Hash Generator. Dan’s Tools.
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