ABSTRACT
This chapter looks at the other extreme and study encryption schemes that are provably secure even against an adversary with unbounded computational power. It discusses the issue of generating randomness suitable for cryptographic applications before returning to a discussion of cryptography per se. The one-time pad was used by several national-intelligence agencies in the mid-20th century to encrypt sensitive traffic. Perhaps most famously, the “red phone” linking the White House and the Kremlin during the Cold War was protected using one-time pad encryption. Shannon’s theorem is useful for deciding whether a given scheme is perfectly secret. The one-time pad is popularly credited to Vernam, who filed a patent on it, but recent historical research shows that it was invented some 35 years earlier.
