Security is one of the most important elements in cryptocurrency, as it negates, or attempts to negate, theft or alteration of any online currency. With everything being on servers and computers instead of in the real world, thievery becomes both more and less difficult. Stealing physical things is usually easier than virtual items, but the anonymity offered by the Internet makes it easier to get away with any illicit activities. Hash algorithms were created to secure data and other online elements, and the three explained here are put in place to do just that.
Developed by the NSA in 2001, the Secure Hash Algorithm (SHA) is a set of cryptographic hash functions, mathematical operations that “hash” data and return a result that a user can compare to a known hash value to determine whether or not the data has been tampered with. SHA-256 is a function included in the SHA-2 group, which improved upon the original SHA-1 group. 256 identifies the function, which is made unique by the number of bits in each word used in the hash, which is 32. It is much more fleshed out than most of the other variations in SHA, which is why it is used mainly in important digital exchanges, such as authenticating Linux software packages and verifying exchanges in cryptocurrencies. Many popular altcoins use SHA-256, as well as Bitcoin itself, to calculate proof-of-work in transactions. This proves that SHA-256 is a powerful and secure algorithm. For more information on the mathematics of SHA-256, you can look here.
Scrypt is key derivation function (KDF) developed by Colin Percival and published in 2012. A KDF is a computationally intensive algorithm that uses passwords to secure data, with the security mainly based around requiring large amounts of memory to complete operations. For a legitimate user, the operation is quick and completes in a little under a second. If a user is trying to attack using a brute-force method, the operation would have to be completed billions of times, which makes it nigh impossible to get through the security system in a reasonable amount of time. This stems from Scrypt’s use of a time-memory trade off, meaning that an attacker will have to either use more memory to complete the operation faster, or use less memory and complete the operation much more slowly. Scrypt’s memory requirement makes it costly to choose either option, deterring attackers. The algorithm is used in proof-of-work verification in cryptocurrency exchanges as well, especially Litecoin, displaying its power and popularity on the digital security stage. For more specific information on the algorithm, you can go here.
The previous two algorithms are much more popular in the cryptocurrency market, and are much older than X11. Introduced slightly over a year ago, X11 is a chained proof-of-work algorithm that uses 11 different rounds of hashes to secure cryptocurrencies and their transactions. Because it was designed specifically for cryptocurrencies (it debuted alongside Darkcoin aka Dash), it has the one of the most sophisticated cryptographic hashes currently in use. It has the advantage of a multi-hash system, meaning that in order for the algorithm to fail, all eleven of its hashes would have to fail at the same time. Taking into account the very minute probability that even one hash would be broken, the chance of the X11 system failing becomes almost zero. Even if the two previous systems failed, any cryptocurrency could move to X11 as a more secure backup. At the moment, Dashcoin is the most popular coin that uses it, but if there are more advances in security breaching in the near future, there may be more currencies moving to X11.