CS191 22 04 22
Zhu, Justin

CS191 22 04 22
Wed, Apr 17, 2019

Diffie, Hellman 1976

Cryptography is an interesting field where preserving security is paramount.

Previously, it appeared that encryption was a luxury for a select few. Distribution of encrypted messages need to be universal as mentioned by Diffie and Hellman. The key may be shorter and easier to hide.

A digital signature is also important in that we can distribute a message or document such that the recipient is confident that no impersonation of the sender is occurring.

Cryptography and number theory are mainstream developments that go hand in hand. Cryptography draws upon the certain ordering of numbers in order to generate a good hash for those numbers.

For many applications, contacts must be made secure against eavesdropping and injection of illegitimate messages. Security problems that lag behind other areas of communication demonstrate the inability of other applications, where unauthorized extraction of information from communications over insecure channels allow a private conversation between two people with no acquaintance to occur.

This is an interesting idea in that a public key distribution system offers a different approach for a secure key distribution channel.

We are also introduced to the notion of signatures, which require the transmission and storage of written contracts.

In order to have a purely digital replacement for the paper, each user should produce a message whose authenticity can be checked by anyone but not produced by the recipient or anybody else.

The privacy system prevents extraction by unauthorized parties from messages over public channels, assuring receiver of the legitimacy of senders. This then means that a channel is public if the security is inadequate for the users’ needs. Public in this sense serves as a euphemism.

Thompson 1984

FORTRAN is the language of choice prior to the C programming language.

C allows a string to construct specific initialized character arrays. ASCII charts are heavily used to convert certain special characters like the “\v” vertical tab character to take on meaning in C.

A deliberate miscompilation is a “Trojan horse.” The compiler matches code in the UNIX “login” command. Replacement code always micompiles.

We should ultimately not trust code that we should not create yourself. This argument ultimately leads Thompson to conclude that the act of breaking into a computer system should have the same social stigma as breaking into a neighbor’s house, a sentiment that simply was not present during that time.