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Overview and evolution of password-based authentication schemes

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Password is the oldest and the most widely used pillar of authentication, and is still being the core of approximately 80% of authentication events in the 21st century Internet. As the data on the Web becomes more valuable, more sophisticated attacks on authentication are being developed. The good thing is that crypto community tries to keep up with the continuously increasing threat surface and provides more advanced authentication techniques with higher security guarantees. However, password is still a solid building block in each of them: the first part of most two-factor authentication schemes is a password challenge, to generate one-time token, you enter a password, to use a hardware device - you enter a password in the device. But is verifying passwords secure? By communicating a password to a verifying party you leak at least some of the password information. Given the long history of password-based authentication schemes we can clearly see that it is rather challenging even to properly implement password verification. The presentation gives an overview of the evolution of password-based authentication schemes and provides comparison between two of the latest ones: socialist millionaires’ protocol and SPAKE2.

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Overview and evolution of password-based authentication schemes

  1. 1. Overview and evolution of password- based authentication schemes Ignat Korchagin
  2. 2. Passwords in Roman Empire Ave, Caesar! http://ancienthistory.about.com/library/bl/bl_text_polybius6.htm • every night the watchword was changed • used a “roundtrip” delivery mechanism with confirmation to distribute the password
  3. 3. Passwords in modern world create password? “hunter2” hehe, no one will ever guess
  4. 4. HTTP basic authentication alice:example.com:hunter2
  5. 5. HTTP basic authentication alice:example.com:hunter2 • simple • password is sent in clear text • HTTPS is needed to protect from eavesdroppers • server DB leak compromises all the passwords
  6. 6. HTTP digest authentication • server stores Hash(alice:example.com:hunter2)
  7. 7. HTTP digest authentication • server stores Hash(alice:example.com:hunter2) GET secret info
  8. 8. HTTP digest authentication • server stores Hash(alice:example.com:hunter2) GET secret info nonce
  9. 9. HTTP digest authentication • server stores Hash(alice:example.com:hunter2) GET secret info nonce cnonce, Hash(Hash(alice:example.com:hunter2),nonce,cnonce)
  10. 10. HTTP digest authentication • passwords are not sent in clear text • protected from replay attacks • servers may store hashes of passwords instead of passwords themselves • server DB leak compromises passwords for specific realm only
  11. 11. HTTP digest authentication • passwords are not sent in clear text • protected from replay attacks • servers may store hashes of passwords instead of passwords themselves • server DB leak compromises passwords for specific realm only BUT…
  12. 12. HTTP digest authentication • still vulnerable to MiTM • still vulnerable to spoofed websites • requires HTTPS • vulnerable to dictionary attacks
  13. 13. HTTP digest authentication • still vulnerable to MiTM • still vulnerable to spoofed websites • requires HTTPS • vulnerable to dictionary attacks From RFC 7616: HTTP Digest Authentication, when used with human-memorable passwords, is vulnerable to dictionary attacks. Such attacks are much easier than cryptographic attacks on any widely used algorithm, including those that are no longer considered secure. In other words, algorithm agility does not make this usage any more secure. As a result, Digest Authentication SHOULD be used only with passwords that have a reasonable amount of entropy, e.g., 128-bit or more. Such passwords typically cannot be memorized by humans but can be used for automated web services. If Digest Authentication is being used, it SHOULD be over a secure channel like HTTPS.
  14. 14. HTTP OAuth auth token GET auth token
  15. 15. HTTP OAuth auth token GET auth token • allows delegations • does not need to use real credentials • needs other methods to authenticate on authorization server • HTTPS is needed to protect from eavesdroppers
  16. 16. HTTPS is hard
  17. 17. HTTPS is hard • problems with mixed content • maybe fixed with implementing proper content security policy
  18. 18. HTTPS is hard • problems with mixed content • maybe fixed with implementing proper content security policy • spoofed websites • similar domain names, same look and feel
  19. 19. HTTPS is hard • problems with mixed content • maybe fixed with implementing proper content security policy • spoofed websites • similar domain names, same look and feel • spoofed certificates • https://thehackerblog.com/keeping-positive-obtaining-arbitrary-wildcard-ssl- certificates-from-comodo-via-dangling-markup-injection/index.html
  20. 20. HTTPS is hard • problems with mixed content • maybe fixed with implementing proper content security policy • spoofed websites • similar domain names, same look and feel • spoofed certificates • https://thehackerblog.com/keeping-positive-obtaining-arbitrary-wildcard-ssl- certificates-from-comodo-via-dangling-markup-injection/index.html • compromised keys and certificates • certificate revocation is hard
  21. 21. Can we do better?
  22. 22. Socialist millionaires • Socialist millionaire problem is a way for two millionaires to check whether their wealth is equal
  23. 23. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y.
  24. 24. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2a, G3a, G2b, G3b
  25. 25. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb
  26. 26. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb
  27. 27. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb
  28. 28. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb a3 * Rb = b3 * Ra = (Pa - Pb) + (a3 * b3 * (x - y)) * G2
  29. 29. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb a3 * Rb = b3 * Ra = (Pa - Pb) + (a3 * b3 * (x - y)) * G2
  30. 30. Socialist millionaires • Socialist millionaire problem is a way for two millionaires to check whether their wealth is equal • can be used to verify whether two parties posses the same secret • a passive attacker learns nothing about the protocol and its outcome • MiTM can do no better than passive attacker except disrupting the communication channel • even if one of the parties is dishonest, he learns nothing more that the protocol outcome • unlike most other zero-knowledge proofs requires O(1) protocol iterations • is adopted and has good history
  31. 31. OTR SMP • Uses 1536-bit group calculations
  32. 32. OTR SMP • Uses 1536-bit group calculations • BUT: LogJam!
  33. 33. OTR SMP • Uses 1536-bit group calculations • BUT: LogJam! • 512-bit broken • 1024-bit probably • 1536-bit is very close!
  34. 34. Themis SMP vs OTR SMP • Improving SMP • moved all cryptographic operations in ECC domain • modern (boring) cryptography (ed25519) • timing attacks protection • fast and performant • reduced memory footprint • support for many high-level languages • simple API • GitHub: https://github.com/cossacklabs/themis
  35. 35. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w.
  36. 36. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y
  37. 37. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y T, S
  38. 38. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S
  39. 39. SPAKE2 • PAKE - password-authenticated key agreement • basic SPAKE2 requires only 1 roundtrip • simple, requires small number of asymmetric cryptographic operations • easy to implement • provides a negotiated secret key as a protocol outcome
  40. 40. SPAKE2 • PAKE - password-authenticated key agreement • basic SPAKE2 requires only 1 roundtrip • simple, requires small number of asymmetric cryptographic operations • easy to implement • provides a negotiated secret key as a protocol outcome • Example: SPAKE2 (https://tools.ietf.org/html/draft-irtf- cfrg-spake2-03)
  41. 41. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • provides mutual authentication
  42. 42. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • provides mutual authentication • protected from MiTM
  43. 43. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • provides mutual authentication • protected from MiTM • requires 2 roundtrips
  44. 44. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb
  45. 45. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S
  46. 46. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S Key confirmation?
  47. 47. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • slower • provides mutual authentication • protected from MiTM • requires 2 roundtrips • faster
  48. 48. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • slower • ~30 times slower in pure C • provides mutual authentication • protected from MiTM • requires 2 roundtrips • faster • ~30 times faster in pure C
  49. 49. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • slower • ~30 times slower in pure C • ~3 times slower in Python • provides mutual authentication • protected from MiTM • requires 2 roundtrips • faster • ~30 times faster in pure C • ~3 times faster in Python
  50. 50. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • slower • ~30 times slower in pure C • ~3 times slower in Python • negotiates 2 shared secrets • provides mutual authentication • protected from MiTM • requires 2 roundtrips • faster • ~30 times faster in pure C • ~3 times faster in Python • negotiates 1 shared secret
  51. 51. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb
  52. 52. Socialist millionaires • EC curve: G - base point, n - order of G • Alice and Bob have x and y respectively. Both want to know whether x==y. Generate a2, a3, s G2a = a2*G G3a = a3*G Generate b2, b3, r G2b = b2*G G3b = b3*G G2 = a2*G2b G3 = a3*G3b Pa = s*G3 Qa = s*G + x*G2 G2 = b2*G2a G3 = b3*G3a Pb = r*G3 Qb = r*G + y*G2 Ra = a3*(Qa-Qb) Rb = b3*(Qa-Qb) a3*Rb == Pa-Pb b3*Ra == Pa-Pb G2a, G3a, G2b, G3b Pa, Qa, Pb, Qb Ra, Rb
  53. 53. SMP vs SPAKE2 SMP SPAKE2 • provides mutual authentication • protected from MiTM • requires 3 roundtrips • slower • ~30 times slower in pure C • ~3 times slower in Python • negotiates 2 shared secrets • provides zero-knowledge guarantee • provides mutual authentication • protected from MiTM • requires 2 roundtrips • faster • ~30 times faster in pure C • ~3 times faster in Python • negotiates 1 shared secret • has some implementation caveats
  54. 54. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S
  55. 55. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S
  56. 56. SPAKE2 • EC curve: G - base point, n - order of G, M,N - known fixed points on the curve • Alice and Bob know w. Generate x X = x*G T = w*M + X Generate y Y = y*G S = w*N +Y K = x*(S - w*N) K = y*(T - w*M) T, S To successfully complete the protocol: • the peer may not even know w (the real secret information) • but only w*M and w*N (its public derivatives)
  57. 57. Possible use-cases
  58. 58. Possible use-cases
  59. 59. Possible use-cases Encrypted communication (K1) • Automatic key rotation for long-lived encrypted connections
  60. 60. Possible use-cases SMP (or SPAKE2 with confirm) Encrypted communication (K1) • Automatic key rotation for long-lived encrypted connections
  61. 61. Possible use-cases SMP (or SPAKE2 with confirm) Encrypted communication (K1) • Automatic key rotation for long-lived encrypted connections save negotiated key
  62. 62. Possible use-cases SMP (or SPAKE2 with confirm) Encrypted communication (K1) Encrypted communication (K2) • Automatic key rotation for long-lived encrypted connections save negotiated key
  63. 63. Conclusions • Zero-knowledge protocols are useful building blocks for enhanced security and privacy preserving protocols • They can be useful in a scenario where one of the protocol participants may be malicious • You may use SPAKE2 for many real world tasks, but you have to be aware of the caveats • Socialist millionaire protocol provides more security guarantees, although with some performance penalty
  64. 64. Links • Paper: https://www.cossacklabs.com/files/secure- comparator-paper-rev12.pdf • SMP code: https://github.com/cossacklabs/themis • SPAKE2 code: https://boringssl.googlesource.com/ boringssl/+/master/crypto/curve25519/spake25519.c • sctest.c: https://gist.github.com/secumod/ d3a064ee93e3eda74aebd379e60ede66 • spake2test.c: https://gist.github.com/secumod/ 5c35c067a4e25fbe038f09a2706b236b
  65. 65. Thank you! Questions?

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