Argon2 is a key derivation function. It is designed to take a password (and some salt), and generate a desired number of pseudo-random bytes. Like scrypt, it is also memory hard, meaning it is designed thwart implementations on ASICs and GPUs. It was selected as the winner of Google's Password Hashing Competition in 2015.
To hash a pssword using default cost factors:
hash := TArgon2.HashPassword('correct battery horse staple'); //using default cost factors
-
To hash a password specifying your own cost factors:
hash := TArgon2.HashPassword('correct battery horse staple', 1000, 128*1024, 1); //Iterations=1000, Memory=128MB, Parallelism=1 -
To verify a password:
isPasswordValid := TArgon2.CheckPassword('correct battery horse stapler', expectedHash, {out}passwordRehashNeeded);
By convention Argon2 outputs a password hash as string in the form:
$Argon2id$v=[version]$m=[memoryKB],t=[type],p=[parallelism]$[salt]$[hash]
$argon2i$v=19$m=65536,t=2,p=4$c29tZXNhbHQ$VGhpcyB3YXMgb25seSBhbiBleGFtcGxlLCBpIGRvbid0IGFjdHVhbGx5IGhhdmUgYSB2YWxpZCBpbXBsZW1udA==
The parts of the string are:
| Value | Meaning | Notes |
|---|---|---|
| argon2id | Hash algorithm | "argon2id", "argon2d", "argon2i" |
| v=19 | Decimal coded version | Default is 0x13, which is 19 decimal |
| m=65536 | Memory size in KiB | Valid range: 8*Parallelism .. 0x7fffffff, and must be a power of two |
| p=4 | Parallelization Factor | 1-0x00ffffff |
| salt | base64 encoded salt | 0-16 bytes decoded |
| hash | base64 encoded hash | 32-bytes |
Because the four argon parameters are stored in the returned string, argon2 password hashes are backwards and forwards compatible with changing the factors. It also makes Argon2 extraordinarily convenient, in that a random salt is automatically generated and stored for you (you don't have to worry about storing it in a database or retrieving it).
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