6.805/6.806/STS.085, Ethics and Law on the Electronic Frontier Lecture 6: Technology-driven Public-Private Boundary Shifts Lecturer: Hal Abelson Encryption Review of how encryption technology works. We will discuss the period of 1980 – 2001 really transformed a military, weapons technology to an everyday commonplace use. Really think about encryption as a policy stresses that are related to introduces new technology. Pitfalls of tech and policy -The word “privacy” has certain associations you make to it, none of them has the internet really associated with it. - About 10 yrs. ago the word “electronic mail” had no real meaning because no one really used it. - The image of a trusted mail carrier is not the image that we have when we speak of electronic mail and encryption Confidentiality – you care about only the intended recipient receives the message Authentication Integrity – how do you know that someone didn’t intercept the message and Non-repudiation – can’t later deny that you received the message This is a review for those that took encryption. These are referred to as digital signatures 1. Pre-historic cryptography (pre 1970s): 2. Public key 3. Policy of cryptography Cryptography ca 1900 BC This is the earliest believed formed of cryptography that people have found—heiroglyphics. Geoffrey Chaucer was a poet and astronomer. Also wrote the first scientific manual in English Treatise on the Astrolabe. In part of this book, he encrypted. (class exercise) Chaucer used a format called the substitution cipher. Simple or monoalphabetic substitution occurs when you always replace in the same way. Julius Ceasar used substitution cipher where you shift everything by the same length to substitute.In the 9th century, Yaqub wrote a book now know as Frequency analysis. (Graph of average frequency of letters in English.) This is a technique since the 9th century. A thousand years later, this form of encryption was still being used which is amazing. People still use insecure methods of encryption. If you go on the Internet (less than 5 years ago), some companies are still marketing insecure or bad encryption products. *Vigenere Encryption Vigenere popularized this type of encryption, but it was actually created by Alberti. The blue letters are the key. “a” goes to “S”, b goes to “O”….and you cycle through each substitution. This turned out to be a major breakthrough in encryption for 500 years, and was considered to be the unbreakable encryption scheme. In fact, it was broken in the middle of the 19th century. *Breaking Vigenere Turn this into n-different frequency distribution problems since the English language has a natural length. The hard part is finding the length of the key. At the end of the 1920’s, most countries had black-jammers that were math chambers to break encryption. Friedman invented the Index of Coincidence to break the encryption. Nobody knew that Babbage had actually broken the Vigenere code until the 1920s since he didn’t announce that he broke it. Many people that do the work actually don’t get the credit because their work ends up being classified. Key is as long as the message – one time pad Only proven secure encryption is the one-time pad, provided that you choose the key randomly and use it only once. But work is being done currently to find something more secure. The Venona Project originated in 1943. Lots of examples of the one-time pad. Claude Shannon – hero of information theory Shannon invented the word the “bit.” Shannon also made the first formal definition of what it means to be secure, or encryption. Results of “Perfect Secrecy” from Shannon’s 1949 paper.The really classified things right now are the ways and methods to generate random pads. It’s actually hard to make really good one-time pads. There’s now a stream encryption that we use today that is the bit analog of Vigenere. DES (Data Encryption Standard) is now becoming obsolete. The NSA tweaked the algorithm to make it more secure. For DES, you break the message into blocks of 64-bits and then do an S-box transformation (based on a 56-bit key) and then put it back together. This is pretty efficient since it is just scrambling and can be easily be decoded. Nicely designed so easy to undo. Security of DES: The only way to crack it is basically brute force. Try all the keys! In 1965, 2^56 was a pretty large number of keys. Not so much now. The gov. was strong-arming people to discouraging using anything other than DES. NIST (National Institute of Standards and Technology). Kerkhoffs’s Principle: Articulated by Belgium linguist that wrote a guidebook on the good properties of cryptographic systems. One of the principles is design the system so that only a tiny bit of information that needs to be secure, then this is a better design. The security should reside in the choice of key rather than in obscure design features. Andrew “Bunnie” Huang – broke the encryption on the XBox. Digital Millenium Copyright Act prevents people from publishing or disseminating information about copyrightable material. These early encryption principles don’t work well for the internet. Great Idea: Can create a shared key with people that have never met before or never communicated and made no prior arrangements. Cryptosystems Various types of attacks: Chosen plaintext- 300 of the same character Rubber hose – beat people with the rubber hose None of this is adequate for Internet applications because you have to meet to exchange the key. Diffie was an MIT undergrad and met up with Marty Hellman, who was working at Stanford. Ralph Merkle was a grad student at Berkeley. Merkle was probably the person with the idea behind public-key encryption, but Hellman and Diffie wrote the algorithm. They published the absolute break-through paper in 1976. Only about 8 years ago, it was discovered that in 1973-74 Clifford Cocks and Malcolm Williamson were doing secret work in the British Intelligence. Basic Idea of Diffie-Hellman-Merkle:Idea: How can you exchange secret information even if everyone can hear what you say to one another? Alice will compute secret information on only what she knows Bob will compute secret information only on what he knows. At the end, there will be a secret number that only Alice and Bob will know. General Approach is to use a one-way function. On one side of the