Implementing-cryptography-using-python

32 Chapter 2 ■ Cryptographic Protocols and Perfect Secrecy
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Gain an understanding of the one-time pad
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Create message secrecy using the binary XOR operator
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Gain an understanding of cryptographic hashes
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Explore the basics of Claude Shannon’s theorem
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Explore the concepts of perfect forward secrecy
The Study of Cryptology
The term cryptology, which was first used in 1844, means the study of codes and
the practice or art of writing or solving them. The word originates from the
Greek words kryptós, meaning “hidden secret”; graphein, meaning “to write”; and
logia, meaning “to study.” It has become a much-researched field that focuses
on techniques for securing communications from eavesdroppers.
Cryptology’s focus is in the construction and analysis of protocols that
prevent any person or system from decrypting messages without authorization.
Cryptology helps ensure the core tenets of cybersecurity by providing confidentiality,
integrity, authentication, and nonrepudiation. We will explore how we
use cryptology for each of these using Python as we move through this book.
For now, the important takeaway is that the study of cryptology is broken down
into two fields: cryptography and cryptanalysis.
Understanding Cryptography
Specifically, cryptography is the science of secret writing with the goal of hiding
the meaning of the message. Cryptography is further broken down into
cryptographic protocols, symmetric algorithms, and asymmetric (or public-key)
algorithms.
Cryptographic protocols, also known as security or encryption protocols,
consist of a well-defined series of steps and message exchanges between several
entities in order to achieve a specific security objective. Cryptographic protocols
should encapsulate a number of properties in order to be viable:
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The protocol must be known by each party involved, and each party must
know the well-defined steps to follow in advance of the protocol’s use.
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The protocol must be unambiguous; every step is well-defined and easy
to understand.
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The protocol must be followed by each party involved.
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The protocol must also be complete.
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The protocol must not give away any details about the message.