Bcrypt

From Wikipedia: https://en.wikipedia.org/w/index.php?title=Bcrypt&oldid=1232137191#Description

The input to the bcrypt function is the password string (up to 72 bytes), a numeric cost, and a 16-byte (128-bit) salt value. The salt is typically a random value. The bcrypt function uses these inputs to compute a 24-byte (192-bit) hash. The final output of the bcrypt function is a string of the form:

$2<a/b/x/y>$[cost]$[22 character salt][31 character hash]

For example, with input password abc123xyz, cost 12, and a random salt, the output of bcrypt is the string

$2a$12$R9h/cIPz0gi.URNNX3kh2OPST9/PgBkqquzi.Ss7KIUgO2t0jWMUW
\__/\/ \____________________/\_____________________________/
Alg Cost      Salt                        Hash

Where:

• $2a$: The hash algorithm identifier (bcrypt)
• 12: Input cost (2¹² i.e. 4096 rounds)
• R9h/cIPz0gi.URNNX3kh2O: A base-64 encoding of the input salt
• PST9/PgBkqquzi.Ss7KIUgO2t0jWMUW: A base-64 encoding of the first 23 bytes of the computed 24 byte hash

The base-64 encoding in bcrypt uses the table ./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789, which differs from RFC 4648 encoding.