This chapter introduces cryptography from information security phase rather than from deep mathematical and theoretical aspects, along with cryptography application in information security. The chapters introduce classical cryptography, block, stream cipher, and public key family, and with the most advance systems as elliptic curve, digital signature, cryptography key managements, and the last part of the chapter are the cryptography application in protocols, communications, e-mails, and the most advance research topics.
The word cryptography means “secret writing.” Some define “cryptography” as “study of mathematical techniques”. Cryptography is a function which transfer “plain text” pt in to “ciphertext” ct, and decryption is the inverse function which transfer “ciphertext” into “plain text.”
The cryptography goals are: Privacy or confidentiality, data integrity, authentication and nonrepudiation.
Key Terms in this Chapter
Public Key Cryptography (PKC): Also known as asymmetric cryptography, it uses two keys—a “public key” and a “private key” —to implement an encryption.
Symmetric Key Cryptography: Uses identical cryptography key for encryption and decryption.
Digital Signature: Also called electronic signature, it is used to indicate that the plain text or file that it is attached to an electronic mail is originated by the sender. The process has three parts: Key Generation, Signature, and Verification. There are other terms comes in association with Digital Signature, such as Digital Certificates (DC).
Stream Cipher: Also called one time pad system (Vernam Cipher), it is a symmetric type, where plain text bits are combined with a key stream bits using exclusive, or XOR, operation.
Elliptic Curve Cryptography (ECC): An approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields.
Block Cipher: A symmetric key cipher which operates on fixed-length groups of bit.
Cryptography: The “Study of mathematical techniques” and its goals are: Confidentiality, Data Integrity, Authentication and Nonrepudiation.
Asymmetric Key Cryptography: Uses different cryptography key encryption and decryption.