The document provides an overview of digital signatures, highlighting their purpose in ensuring authentication, integrity, and non-repudiation of digital messages. It explains key terminology, algorithms for signing and verification, and discusses major digital signature schemes like DSA and ECDSA, including their use in bitcoin transactions. Additionally, it offers resources for further reading and exploration of associated cryptographic concepts.

1. Digital Signatures
A mathematical scheme for demonstrating the
authenticity of a digital message or document.
michael.dance@gmail.com
@mikedance

2. Presentation Goals
• Provide a high level overview of digital
signatures
• Define the terminology used for digital
signatures

3. Analogy
A handwritten signature or seal placed on a written
document.

5. Important Distinction

6. A digital signature is
unique to each message
Unlike a physical signature, where the same signature is used for
multiple documents, a digital signature changes with each message.

7. Purpose
What security principles do we achieve with digital
signatures?

8. Authentication
Provides proof that a message was sent by a known
sender.

9. Integrity
The message was not altered in transit.

10. Non Repudiation
The sender cannot deny having sent the message.

11. Terminology

12. Key Generation
An algorithm that outputs a private key (signing key),
and public key (verification key).

13. Signing Key
The private key used to generate a digital signature.

14. Verification Key
The public key available to anyone to verify whether a
digital signature is valid.

15. Signing Algorithm
Given a message, and signing key produces a digital
signature.

16. Signature Verification
Algorithm
Given a message, verification key, and a digital
signature determines whether the message is authentic.

18. Digital Signature
Schemes
What are the main digital signature schemes in use
today?

19. DSA
• Digital Signature Algorithm
• Established by NIST in 1991 as the US
government standard for digital signatures
• Is a variant of the ELGamal Signature Scheme

20. ECDSA
• Elliptic Curve Digital Signature Algorithm
• Used in Bitcoin to transfer funds from one
address to another

21. Bitcoin Usage
• When spending bitcoins, the bitcoin owner
presents their public key, and a signature for the
transaction
• The bitcoin network uses the digital signature
verification algorithm to verify the public key, and
signature are valid

22. Live Demo
https://brainwallet.github.io/#sign

23. What’s Next?
• Hash Functions
• Elliptic Curve Cryptography
• Bitcoin Cryptography Usage

24. Questions?
michael.dance@gmail.com
@mikedance

25. Further Reading
• Brainwallet
• https://brainwallet.github.io/
• Princeton Lecture 1 — Intro to Crypto and Cryptocurrencies
• https://www.youtube.com/watch?v=fOMVZXLjKYo
• Digital Signature Algorithm
• http://en.wikipedia.org/wiki/Digital_Signature_Algorithm
• Elliptic Curve Digital Signature Algorithm
• http://en.wikipedia.org/wiki/
Elliptic_Curve_Digital_Signature_Algorithm