Using Reverse Lookup Tables, you create a lookup table consisting of the password hash of user accounts. Then you use another table which consists of hashes with guessed passwords. Then you compare the two to see if the hashed password of compromised user account matches hashed password in lookup table.

Using Rainbow Tables, it appears to be the same technique except the lookup table is smaller so you can search through them quicker.

What is the real difference between reverse lookup tables and rainbow tables?

  • There is no essential difference. The only distinction tends to be that of "size" (if at all).
    – Oded
    Aug 12, 2014 at 18:37
  • @Oded then why do experts say that you need a salt to solve rainbow table problem, whereas a hash like sha1 can solve reverse lookup table problem, but not rainbow table problem. Aug 12, 2014 at 18:53
  • Where do the experts say that?
    – Oded
    Aug 12, 2014 at 18:53
  • @Oded crackstation.net/hashing-security.htm if the two were virtually the same thing, then there wouldn't be separate names for them. Aug 12, 2014 at 18:55
  • 4
    Rainbow tables are a specific lookup table compression technique so the size of the table is not linear in the number of passwords. Aug 15, 2014 at 8:01

1 Answer 1


Wikipedia explicitly calls out the difference between a rainbow table and a "simple lookup table" as being multiple entries per hash vs. one entry per hash. See the opening paragraph.

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