Key derivation functions such as SCrypt and PBKDF2 are used to turn a user's password into a cryptographic key that can be used to encrypt and decrypt data. The two algorithms are designed to be computationally expensive, making brute-force attacks on large lists of passwords difficult.
SCrypt and PBKDF2 differ significantly in the manner in which they generate keys. To generate keys, PBKDF2 applies a cryptographic function (such as SHA-1 or SHA-2) repeatedly to the password and a salt value. If the number of iterations is increased, the process will become more computationally expensive, but it will also take longer to generate a key.
SCrypt, on the other hand, generates keys using a method called "memory-hardness." A large amount of memory is used to perform calculations, making it more challenging for attackers to use specialized hardware (such as GPUs) to perform brute-force attacks. In addition, SCrypt allows users to specify a larger salt value, which increases the number of possible keys that can be generated and makes precomputation attacks more difficult.
“Memory-hardness is a property of specific cryptographic algorithms that makes them computationally expensive to run, specifically in terms of memory use. Using memory-hardness, the algorithm becomes more resistant to attacks utilizing specialized hardware, such as graphics processing units (GPUs) or application-specific integrated circuits (ASICs), capable of performing many calculations simultaneously and optimized for specific purposes. By increasing the memory requirements of the algorithm, it becomes more difficult for attackers to perform brute-force attacks on these types of hardware.”
Another difference between SCrypt and PBKDF2 is the number of iterations recommended. While PBKDF2 recommends a minimum of 600,000 iterations for adequate security, SCrypt does not make such a recommendation. Instead, it is determined by the cost parameter, which can be adjusted to increase or decrease the computational cost.
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