The art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. Only those who possess a secret keycan decipher (or decrypt) the message into plain text. Encrypted messages can sometimes be broken by cryptanalysis, also called codebreaking, although modern cryptography techniques are virtually unbreakable.

As the Internet and other forms of electronic communication become more prevalent, electronic security is becoming increasingly important. Cryptography is used to protect e-mail messages, credit card information, and corporate data. One of the most popular cryptography systems used on the Internet is Pretty Good Privacy because it’s effective and free.

Cryptography systems can be broadly classified into symmetric-key systems that use a single key that both the sender and recipient have, and public-keysystems that use two keys, a public key known to everyone and a private key that only the recipient of messages uses.

By Webopedia

Cryptography (or cryptology; from Greek κρυπτός, “hidden, secret”; and γράφειν, graphein, “writing”, or -λογία, -logia, “study”, respectively) is the practice and study of techniques for secure communication in the presence of third parties (called adversaries). More generally, it is about constructing and analyzing protocols that overcome the influence of adversaries and which are related to various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation. Modern cryptography intersects the disciplines of mathematics, computer science, and electrical engineering. Applications of cryptography include ATM cards, computer passwords, and electronic commerce.

By Wikipedia


German Lorenz cipher machine, used in World War II to encrypt very-high-level general staff messages

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