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Secure Password Storage

Secure Password Storage. Raspberry Pi Powered NTP Server. Joshua Small https://github.com/technion/lhnskey - Root password generator for CVE-2013-2352. https:// lolware.net/cw.html – Connectwise Password “Encryption” Broken jsmall@lolware.net

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Secure Password Storage

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  1. Secure Password Storage Raspberry Pi Powered NTP Server Joshua Small https://github.com/technion/lhnskey - Root password generator for CVE-2013-2352. https://lolware.net/cw.html – Connectwise Password “Encryption” Broken jsmall@lolware.net DJB’s crypto snake oil competition submission: http://snakeoil.cr.yp.to/submissions.html

  2. Typical Web Sign Up Form

  3. The Problem

  4. Typical User shinycatz.com Email: john@hotmail.com Password: secret User: Oh all they can do is produce fake cats in my name! Mybank.com Email: john@hotmail.com Password: supersecret Unique password – good boy John! shinycatz.com Compromise Attacked notices: “secret” is the password for John’s hotmail User: All he can do is read my email! Hotmail inbox: Welcome to mybank.com Mybank.com: Forgot your password? Click here and we’ll email you a new one

  5. Typical Vendor

  6. Terrible Solution function encryptpass($password) { $key = “omgakey”; Return base64_encode( mcrypt_encrypt( MCRYPT_RIJNDAEL_256, $key, $password, … Function decryptpass($secret) { $key = “omgakey”; …

  7. Comically terrible solution

  8. User Solutions • Lastpass and similar apps • Unique passwords everywhere! • Uptake from users: very low

  9. Hash Algorithms! • MD5: Officially Broken! Do not want! • SHA1: Published 1995, theoretical attack: 2^61 • SHA256: Brute force at 2^128 • This would make SHA256 completely secure for our purposes, for completely random input • But passwords are not random

  10. Key space • One byte stores eight bit of data • But only 96 ASCII characters are printable • That leaves roughly 6.5 bits of entropy per byte • Average password is 6 characters long • That’s only 39 bits of brute force - feasible

  11. Improvements • Stretching: Literally “perform the hash x times” • Salt: incorporate a random string. This prevents “rainbow tables”, ie a big database of precomputed hash values

  12. SHA512crypt • Literally applies the principles of “stretching” and “salting” to SHA512 • Default in several current Linux distributions for passwords in /etc/shadow

  13. Bitcoin • Uses the SHA algorithm • CPU: Core i7 820: 13.8Mhash/s • GPU: GTX295: 120.70Mhash/s • ASIC: Antminer S1: 180,000Mhash/s Source: https://en.bitcoin.it/wiki/Mining_hardware_comparison

  14. Scrypt • Developed by Colin Percival, presented May 2009 • Designed to offer significantly lower advantages to GPU and ASIC devices • Uses a hard to optimise hash function • Is not only computationally hard- but memory hard • Original paper: http://www.tarsnap.com/scrypt/scrypt.pdf • Used in Dogecoin • Dogecoin ASICS pushing 70KHash/s a big deal! • Increasing difficulty doesn’t just slow things down, it can break those ASICS by exceeding their memory

  15. Very short algorithm summary Source: https://tools.ietf.org/html/draft-josefsson-scrypt-kdf-00

  16. Problem: Accessibility • Use in applications: Reference app • Implementation function: • Produces a binary string as output

  17. Introducing libscrypt • Simpler API: • Produces one string containing salt, difficulty operators and hash altogether • Output is already BASE64 encoded, ready for storage • Simple checking function

  18. Accessibility: Platform support • Fedora RPM • Debian (and derivatives) package • FreeBSD ports • OpenBSD ports • Homebrew (OS X) • Tested on ARM (Raspbian) • Tested on IBM s390 for some reason

  19. Difficulties • Potential DoS opportunity • Rate limit • Proof of work • Captcha

  20. Future Improvements • HSM • Polypasshash • Questions?

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