DIGITAL SIGNATURES
By Jonathan Gruber
OUTLINE
• Definition
• How it works
• Common uses
• History
• Ink vs. Digital
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.
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)
HOW IT WORKS FOR SENDER
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
OVERVIEW
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.
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
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
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 EBusiness 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. <http://searchsecurity.techtarget.com/definition/digitalsignature>.