What is cryptography?
As the field of cryptography has advanced, the dividing lines for what is and what is not cryptography have become blurred. Cryptography today might be summed up as the study of techniques and applications that depend on the existence of difficult problems. Cryptanalysis is the study of how to compromise (defeat) cryptographic mechanisms, and cryptology (from the Greek kryptós lógos, meaning “hidden word”) is the discipline of cryptography and cryptanalysis combined. To most people, cryptography is concerned with keeping communications private. Indeed, the protection of sensitive communications has been the emphasis of cryptography throughout much of its history [Kah67]. However, this is only one part of today’s cryptography. Encryption is the transformation of data into a form that is as close to impossible as possible to read without the appropriate knowledge (a key; see below). Its purpose is to ensure privacy by keeping information hidden from anyone for whom it is not intended,
Everyone has secrets; some have more than others. When it becomes necessary to transmit those secrets from one point to another, it’s important to protect the information while it’s in transit. Cryptography presents various methods for taking legible, readable data, and transforming it into unreadable data for the purpose of secure transmission, and then using a key to transform it back into readable data when it reaches its destination. Predating computers by thousands of years, cryptography has its roots in basic transposition ciphers, which assigns each letter of the alphabet a particular value. A simple example is to assign each letter a progressively higher number, where A=1, B=2, and so forth. Using this formula for example, the word “wiseGEEK”, once encrypted, would read “23 9 19 5 7 5 5 11”. During World War Two, machines were invented that made the ciphers more complicated and difficult to break, and today, computers have made cryptography even stronger still. The Secure Socke
Cryptography, to most people, is concerned with keeping communications private. Indeed, the protection of sensitive communications has been the emphasis of cryptography throughout much of its history. As we will see, however, this is only one part of today’s cryptography. Encryption is the transformation of data into some unreadable form. Its purpose is to ensure privacy by keeping the information hidden from anyone for whom it is not intended, even those who can see the encrypted data. Decryption is the reverse of encryption ; it is the transformation of encrypted data back into some intelligible form. Encryption and decryption require the use of some secret information, usually referred to as a key. Depending on the encryption mechanism used, the same key might be used for both encryption and decryption, while for other mechanisms, the keys used for encryption and decryption might be different (see Question 3). But today’s cryptography is more than secret writing, more than encryptio
Coron, J.-S. Security & Privacy, IEEE Volume 4, Issue 1, Jan.-Feb. 2006 Page(s): 70 – 73 Digital Object Identifier 10.1109/MSP.2006.29 Summary: Cryptography’s aim is to construct schemes or protocols that can still accomplish certain tasks even in the presence of an adversary. A basic task in cryptography is to enable users to communicate securely over an insecure channel in a way that guarantees their transmissions’ privacy and authenticity. Providing privacy and authenticity remains a central goal for cryptographic protocols, but the field has expanded to encompass many others, including e-voting, digital coins, and secure auctions. This paper explains what cryptography is about and how we can scientifically justify a cryptographic scheme’s security.
