Implementing-cryptography-using-python

Chapter 2 ■ Cryptographic Protocols and Perfect Secrecy 33
Cryptographic protocols are used in secure application-level data transport
such as Transport Layer Security (TLS), which is used to secure HTTPS web
connections. Another protocol that we will explore later in the chapter is the
Diffie-Hellman key exchange, which is also used by TLS in its secure communications.
Other applications include secret splitting, secret sharing, timestamping,
key escrow, zero-knowledge proofs, blind signatures, electronic money,
and securing elections. The data integrity of the message exchange process is
a critical aspect of the selected protocols; data integrity is a building block for
cryptographic protocols.
Cryptography’s Famous Family: Alice and Bob
Alice and Bob are the world’s most famous cryptographic couple; you will see
references to the dynamic couple through a wide variety of examples inside
this book (see Figure 2.1). Since their inception in 1978, Alice and Bob have at
once been called “inseparable” and been subject of numerous travels, torments,
and even divorces. In the ensuing years, other characters have joined their
cryptographic family. There’s Eve, the passive and submissive eavesdropper;
Mallory, the malicious attacker; and Trent, trusted by all, just to name a few.
Alice and Bob, along with their extended family, were first used to explain how
cryptography works but now have become widely used across engineering and
scientific domains. Alice and Bob have become an archetype of digital exchange
and a lens through which to view broader digital culture.
EVE
FILE
SOURCE
ENCRYPT
DECRYPT
DESTINATION
FILE
ALICE
BOB’S
PUBLIC KEY
ALICE’S
PUBLIC KEY
BOB
Figure 2.1: Alice and Bob