GUESS THE CORRECT LOG CT INSIGHTS 1 2 3 4 5 Content TLS + - - PowerPoint PPT Presentation

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GUESS THE CORRECT LOG CT INSIGHTS 1 2 3 4 5 Content TLS + - - PowerPoint PPT Presentation

Jul 06, 2023 175 likes •733 views

create your own exercise Berkay Kozan, Jan Krol Group 202 GUESS THE CORRECT LOG CT INSIGHTS 1 2 3 4 5 Content TLS + Vulnerabilities CA + Black Tulip How Certificate Transparency Works SCT delivering methods Merkle

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create your own exercise

GUESS THE CORRECT LOG – CT INSIGHTS

Berkay Kozan, Jan Krol Group 202

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Content

⚫ TLS + Vulnerabilities ⚫ CA + Black Tulip ⚫ How Certificate Transparency Works ⚫ SCT delivering methods ⚫ Merkle Tree

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TLS

⚫ Cryptographic protocol ⚫ Secures website-browser connection ⚫ Main cryptographic system that underlies

all HTTPS connections

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TLS

⚫ Cryptographic protocol ⚫ Secures website-browser connection ⚫ Main cryptographic system that underlies

all HTTPS connections

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How can we be sure that we are really connecting to the lab system?

Certificate = public key + domain name

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TLS

⚫ Cryptographic protocol ⚫ Secures website-browser connection ⚫ Main cryptographic system that underlies

all HTTPS connections

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How can we be sure that we are really connecting to the lab system?

Certificate = public key + domain name

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Vulnerabilites of SSL

⚫ Structural flaws ⚫ Vulnerabilities:

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Domain validation

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End-to-end encryption

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Chains of trust set up by certificate authorities

⚫ CT is used to make CAs accountable

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Security Attacks

⚫ Website spoofing ⚫ Server impersonation ⚫ Man-in-the-middle attacks.

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Certificate Authorities

⚫ WE TRUST CAs to issue digital

  • certificates. But should we?

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Black Tulip

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YOU

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Black Tulip

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YOU

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CA handshake

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CA handshake

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CA handshake

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CA handshake

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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CA handshake

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YOU

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How CT Works

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How CT Works

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Log Server

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How CT Works

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Log Server Every new certifacte will be uploaded to the Log Server Watch for:

  • suspicious certificates
  • unauthorized certificates
  • unusual certificate extensions
  • certificates with strange permissions
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CT logs

⚫ CT log = network service which maintains

entries of SSL certificates

⚫ Logs are independent ⚫ Qualities:

− Append-only − Cryptographically assured − Publicly auditable

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CT logs

⚫ CT log = network service which maintains

entries of SSL certificates

⚫ Logs are independent ⚫ Qualities:

− Append-only − Cryptographically assured − Publicly auditable

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thou shalt not hack – RFC 69:62

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SCT

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SCT

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Log Server

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SCT

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Log Server Certificate Authority

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SCT

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Log Server Certificate Submission Certificate Authority

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SCT

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SCT Log Server Certificate Submission Certificate Authority

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SCT

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SCT Log Server Certificate Submission Certificate Authority Promise that the cert will be appended to the log.

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SCT

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SCT Log Server Certificate Submission Certificate Authority Promise that the cert will be appended to the log. Maximum Merge Delay (Appending musst happen within a reasonable time frame)

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SCT

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SCT Log Server Certificate Submission Certificate Authority Promise that the cert will be appended to the log. Maximum Merge Delay (Appending musst happen within a reasonable time frame)

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SCT Delivering Methods: X.509v3 Extension

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SCT Delivering Methods: X.509v3 Extension

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Client (browser)

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SCT Delivering Methods: X.509v3 Extension

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fingernails4cash.com Client (browser)

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SCT Delivering Methods: X.509v3 Extension

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Certificate Authority fingernails4cash.com Client (browser)

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Authority fingernails4cash.com Client (browser)

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Submission (Precertificate) Certificate Authority fingernails4cash.com Client (browser)

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Submission (Precertificate) Certificate Authority fingernails4cash.com Client (browser) SCT

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Submission (Precertificate) Certificate Authority fingernails4cash.com Client (browser) SCT Certificate Issuance (SSL cert w/SCT)

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Submission (Precertificate) Certificate Authority fingernails4cash.com Client (browser) SCT Certificate Issuance (SSL cert w/SCT) TLS handshake (SCT embedded cert)

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SCT Delivering Methods: X.509v3 Extension

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Log Server Certificate Submission (Precertificate) Certificate Authority fingernails4cash.com Client (browser) SCT Certificate Issuance (SSL cert w/SCT) TLS handshake (SCT embedded cert)

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Merkle Tree

  • Simple binary tree
  • Once an hour a log server

appends all new certs to its log

  • Consistency Proof
  • Merkle Audit Proof

17 a b c d s t c1 c2 c3 c4

Merkle Tree Hash Node Hash Leaf Hash Certificate

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Merkle Audit Proof

18 a b c d s t c1 c2 c3 c4

Audit Proof

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Learning Goals

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The Following Learning Goals are Covered in the Lecture PreLab Lab Students understand CT operation X X X Students understand the vulnerabilities of SSL. X X Students understand how log proof works X X Students will fetch SCTs from TLS extension and analyze it X X Students write code to do an InclusionProof that verifies that a cert is logged based on SCT X Students write code to perform an Merkle Audit Proof X

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Teaser Practical Part

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Team

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References

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https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Symantec_logo10.svg/20 00px-Symantec_logo10.svg.png

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https://upload.wikimedia.org/wikipedia/commons/7/7d/Comodo-Secure-DNS.jpg

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https://upload.wikimedia.org/wikipedia/commons/thumb/4/48/DigiCert_logo.svg/2000p x-DigiCert_logo.svg.png

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https://pixabay.com/de/jesus-christus-religion-christentum-1340401/

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https://www.certificate-transparency.org/how-ct-works

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https://www.certificate-transparency.org/log-proofs-work

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Microsoft Office inbuilt Pictograms

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Unsplash.com (License: All photos published on Unsplash can be used for free. You can use them for commercial and noncommercial purposes. You do not need to ask permission from or provide credit to the photographer or Unsplash, although it is appreciated when possible.)

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Summary

⚫ TLS + Vulnerabilities ⚫ CA + Black Tulip ⚫ How Certificate Transparency Works ⚫ SCT delivering methods ⚫ Merkle Tree

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