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At one bit per FF you're going to need quite a few of them. You would be better off using a microcontroller for that purpose. If you still insist on a discrete logic implementation then I would suggest a gate array.

 

how bits is the password?

 

a bit can store 2 states.
a byte stores 256 states.
The ascii system is at least 7 bits long, typically 8.

So to store 1 character, you need at least 4 7474's. you could use 1 74xxx73 (8-bit latch/flip-flop), but the best way to go is to use a microcontroller.