Which is least secure method of authentication?

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Tags

1. #thing
2. #method
3. #passwords
4. #replicate
5. #secure
6. #encrypted
7. #least
8. #physical
9. #compromised
10. #retina
11. #fingerprint
12. #which
13. #easily
14. #following
15. #authentication
16. #explanation
17. #telnet