PBKDF2 is used to iterate the password multiple times using the specified hash function, thereby increasing the cost of cracking the password digests after the database is leaked.
Because it is natively supported by modern browsers and requires only a few lines of code.
If we use other hash algorithms, more than half of the performance will be lost in the JavaScript/WebAssembly VM.
Since PBKDF2 does not support concurrency, it cannot fully utilize multi-core CPU resources.
So some improvements can be made: we create multiple threads, each thread calculates PBKDF2 with different parameters, and finally merge the individual results together:
# parallel
for i = 1 to N
dk[i] = pbkdf2(pwd, i + salt, iter)
reuslt = hash(dk[1] + dk[2] + ... + dk[N])In this way, the hash time on the browser side will not change, but N times of computing resources will be consumed during cracking.
https://etherdream.github.io/parallel-pbkdf2/
We use <i, SiteId, User> as salt. SiteId is a fixed UUID that identifies different sites, preventing attackers from using shared rainbow tables. If an attacker generates rainbow tables for each site, the cost will be very high.
Modern browsers support PBKDF2, but some browsers have issues.
Firefox's PBKDF2 is not fully optimized and has only half the performance of other browsers; Chrome cannot run PBKDF2 in parallel.