1. By Jonathan Gruber DIGITAL SIGNATURES

2. OUTLINE Definition How it works Common uses History Ink vs. Digital

3. DEFINITION OF DIGITAL SIGNATURE A mathematical scheme for demonstrating the authenticity of a digital message or document Digital signatures are easily transportable Cannot be imitated by someone else Can be automatically time-stamped.

4. HOW IT WORKS FOR SENDER Copy-and-paste the contract into an e-mail note Using special software, a message hash (mathematical summary) of the contract is obtained A private key that has previously been obtained from a public-private key authority is used to encrypt the hash The encrypted hash becomes digital signature of the message (different each time)

5. HOW IT WORKS FOR SENDER

6. HOW IT WORKS FOR RECIPIENT Recipient makes a hash of the received message Public key is used to decrypt the message hash or summary If hashes match, the received message is valid

7. OVERVIEW

8. COMMON USES By professionals to send official documents Clients to their lawyers, doctors, etc. Universities in official transcripts The U.S. Government for bills, laws, etc.

9. HISTORY In 1976, Whitfield Diffie and Martin Hellman first described the notion of a digital signature scheme In 1988, Shafi Goldwasser, Silvio Micali, and Ronald Rivest became the first to rigorously define the security requirements of digital signature schemes In 2000, Global and National Commerce Act signed by Pres. Clinton says E-Signatures are legally equivalent to hand-written signatures

10. INK VS. DIGITAL SIGNATURES Ink signatures are very hard to replicate well enough that they can resist scrutiny by an expert Digital signatures cannot be copied Ink signatures can be copied manually or digitally, but still will not hold up to scrutiny Digital signatures can be applied to an entire document Ink signatures usually only on last page

11. BIBLIOGRAPHY "Digital Signature And Watermark Methods For Image Authentication Using Cryptography Analysis." Signal & Image Processing: An International Journal 2.2 (2011): 170-179. Computers & Applied Sciences Complete. Web. 29 Nov. 2011. Jilovec, Nahid. "E-Signatures For Paper Reduction And Process Automation." System Inews 379 (2011): 19-22. Computers & Applied Sciences Complete. Web. 29 Nov. 2011. Gupta, Alok, Y. Alex Tung, and James R. Marsden. "Digital Signature: Use And Modification To Achieve Success In Next Generational E- Business Processes." Information & Management 41.5 (2004): 561. Computers & Applied Sciences Complete. Web. 2 Dec. 2011. Kuechler, William, and Fritz H. Grupe. "Digital Signatures: A Business View." Information Systems Management 20.1 (2003): 19. Computers & Applied Sciences Complete. Web. 29 Nov. 2011. "What Is Digital Signature (electronic Signature)? - Definition from Whatis.com." Information Security Information, News and Tips - SearchSecurity.com. TechTarget, Oct. 2000. Web. 02 Dec. 2011..