Hacking Cryptography for Defenders - Ruben Gonzalez - DCTAC2025

Name of Training: Hacking Cryptography for Defenders
Trainer(s): Ruben Gonzalez and Aaron Kaiser
Dates: November 3-4, 2025
Time: 8:00 am to 5:00 pm 
Venue: TBD
Cost: $2,200

Course Description: 

Crypto related bugs are super common. OWASP even ranks "Cryptographic Failure" as the second most common security vulnerability class in software. Yet, very often these vulnerabilities are overlooked by developers, code auditors and blue teamers. Because, let's face it: Nobody knows how cryptography works.

During the course you will:

• Understand how modern cryptography works.
  
• Find common crypto vulnerabilities in real software.
  
• Experience crypto exploits for real software and IoT devices and learn how they could have been avoided.

Using case studies from our own pentesting and red teaming engagements, we'll introduce core concepts of applied cryptography and how they fail in practice.

This course will teach you how applied cryptography works, how it's commonly misused in the field and how this leads to exploitable bugs. By the end of the course you will be among a very select group of people who can identify, avoid and fix vulnerabilities in code that uses cryptography.

No prior knowledge required!

Key Learning Objectives:

• Learn how modern cryptography operates.
  
• Learn what kind of guarantees are given by certain primitives, and which aren't.
  
• Understand how crypto primitives are combined into protocols.
  
• Learn how cryptography is often misused in practice and how this is exploited and can be avoided.
  
• Understand exploits for systems using cryptography in an inappropriate way and how to counter them.
  
• Evaluate program code that uses cryptography for proper usage.
  Identify cryptographic schemes and potential vulnerabilities in black-box tests.
  

Course Outline: 

• Introduction to Cryptography
  
  • Basic Terminology
    
  • Security Guarantees
    
  • Composition of Primitives
    
• Attack Categorization
  
  • Security Objectives and their Relation to Cryptography
    
  • Attack Categorization
    
• Working with Crypto Tools
  
  • Introduction to Cyber Chef
    
  • Crypto tools: CryCry Toolkit and OpenSSL
    
  • Challenge Lab: CryCry, OpenSSL and Cyber Chef
    
• Hacking Encryption
  
  • Stream Ciphers
    
    • Introduction to Stream Ciphers
      
    • Real World Examples of Vulnerabilities
      
    • Attacks on Stream Cipher Uses
      
    • Challenge Lab: Stream Ciphers
      
  • Block Ciphers
    
    • Introduction to Block Ciphers
      
    • Modes of Operation
      
    • Real World Examples of Vulnerabilities
      
    • Attacks on Block Cipher Uses
      
    • Challenge Lab: Block Ciphers
      
• Hash Functions
  
  • Introduction to Hash Functions
    
  • Real World Examples of Vulnerabilities
    
  • Password Storage & Cracking
    
  • Challenge Lab: Hash Functions and PW Cracking
    
• Message Authentication Codes and Authenticated Encryption
  
  • Introduction to Message Authentication Codes
    
  • Pitfalls on Trivial Constructions
    
  • Real World Examples of Vulnerabilities
    
  • Challenge Lab: MACs and AuthEnc
    
• Attacks on Entropy and Randomness
  
  • Generating Secure Keys with OS Entropy Pools
    
  • Misuse of Pseudo Random Number Generators
    
  • Backdoors and Cleptography
    
  • Real World Examples of Vulnerabilities
    
  • Challenge Lab: Keys and Randomness
    
• Asymmetric Crypto with RSA and ECC
  
  • Introduction to RSA and ECC
    
  • Key Formats
    
  • Key Sizes and Brute Force
    
  • Real World Examples of Vulnerabilities
    
  • Challenge Lab: RSA and ECC
    
• Public Key Infrastructure and Certificates
  
  • Introduction to Certificates
    
  • x509 Certificate Structure and Features
    
  • Common Certificate Pitfalls
    
  • Chain of Trust and PKI services
    
  • TOFU Principle and Man-In-The-Middle Threats
    
  • Challenge Lab: Certificates and PubKeys
    
• TLS and Friends
  
  • Introduction to TLS and Similar Protocols
    
  • TLS Security parameters
    
  • Exploiting a Man-In-The-Middle position for TLS and VPN
    
  • Intercepting and Decrypting TLS Traffic for Application Testing
    
  • Defeat Public Key Pinning with Dynamic Instrumentation
    
  • Challenge Lab: Intercepting TLS
    
• JWTs and JOSE
  
  • Introduction to JSON Web Tokens and Javascript Object Signing and Encryption
    
  • Real World Examples of Vulnerabilities
    
  • Challenge Lab: Exploiting JWT
    
• Passkeys, WebAuthn, FIDO and 2nd Factor Solutions
  
  • Introduction to Password-Less Authentication
    
  • TOTP Algorithms and Seeds
    
  • Passkeys, FIDO2 and WebAuthn
    
  • Footguns and Examples of Vulnerabilities
    
• Post-Quantum Cryptography
  
  • Introduction to Post-Quantum Algorithms
    
  • Post-Quantum Signatures and KEMs
    
  • Upcoming Post-Quantum Standards
    
  • Challenge Lab: OpenSSL with Post-Quantum
    
• Farewell
  
  • Outlook on Future Developments
    
  • Presentation of Take Home Challenges
    
  • Recap

Difficulty Level:

Beginner to intermediate

Suggested Prerequisites:

This is a beginner to intermediate course. Students should be familiar with at least one scripting language and have a basic understanding of computer networks.

The contents are compressed, but no prior knowledge of cryptography is needed. Every subject is introduced before attacks are presented.

What Students Should Bring:

Participants should bring a laptop with a modern browser to join the virtual learning environment.

Trainer(s) Bio:

Ruben Gonzalez (Lead Trainer)

• 10 years in offensive security research
  
• Security Researcher and Trainer at Neodyme
  
• Auditor of crypto code for multiple large industry projects
  
• Part-time PhD candidate for applied cryptography at the Max Planck Institute
  
• Multi-time DEFCON CTF, Hack-A-Sat, HITB ProCTF and Google CTF finalist
  
• Founder and Chair of the RedRocket Hacking Club
  
• Linkedin: https://www.linkedin.com/in/rugond/

Aaron Kaiser (Support Trainer)

• 3 years in offensive security research
  
• Cryptography Auditor at Neodyme
  
• PhD candidate for Applied Cryptography
  
• Multi-time DEFCON CTF finalist
  

Registration Terms and Conditions: 

Trainings are refundable before October 2, 2025, minus a non-refundable processing fee of $250.

Trainings are non-refundable after October 2, 2025.

Training tickets may be transferred. Please email us at training@defcon.org for specifics.

If a training does not reach the minimum registration requirement, it may be cancelled. In the event the training you choose is cancelled, you will be provided the option of receiving a full refund or transferring to another training (subject to availability).

Failure to attend the training without prior written notification, will be considered a no-show. No refund will be given.

By purchasing this ticket you agree to abide by the DEF CON Training Code of Conduct and the registration terms and conditions listed above.

Several breaks will be included throughout the day. Please note that food is not included.

All courses come with a certificate of completion, contingent upon attendance at all course sessions.