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TopBackground: Cryptography Main Techniques
In this section, the definition, overview of the main techniques and the literature review of the related works are presented.
Cryptography
Cryptography is the science of mapping the plaintext into ciphertext and vice versa (called encryption and decryption) by using algorithms with mathematical functions. Cryptography provides the services of confidentiality, authenticity, integrity, non-repudiation and secrecy. In general, there are three types of cryptographic primitives: secret key (or symmetric) cryptography, public-key (or asymmetric) cryptography and un-keyed (hash functions).
Symmetric (Secret Key) Cryptography
A single key is used for both encryption and decryption which transforms plaintext into ciphertext using a secret key and an encryption algorithm. Using the same key and a decryption algorithm, the plaintext is recovered from the ciphertext (Stallings, 2006).
Symmetric key cryptography is categorized as stream cipher and block cipher. They provide data confidentiality by encryption. Stream ciphers partition the text into small blocks which operate on a single bit (byte or computer word) at a time and implement some form of feedback mechanism so that the key is constantly changing (a different key is generated for each block). A block cipher partition the text into relatively large (e.g., 128 bits) blocks and encrypts one block of data at a time using the same key on each block. Algorithms of symmetric key cryptosystems are DES, Triple DES, AES and so on.
Key Terms in this Chapter
Cryptography: The science of information security with the study of mathematical techniques. Cryptography is the scrambling of plaintext into ciphertext (called encryption) and then back again (called decryption) and has the ability to securely store and transfer sensitive information. The goal of cryptography is to address the four areas of confidentiality, integrity, non-repudiation and authentication in both theory and practice.
Integrity: Guarding against improper information modification or destruction, and includes ensuring information has not been altered by unauthorized or unknown means.
Information Security: Protecting information against unauthorized access or modification to ensure the availability, confidentiality and integrity of information whether in storage, processing or transit.
Decryption: Is simply the reverse of encryption, a process of converting encrypted data (ciphertext) back into its original form (plaintext) using a cryptographic algorithm and key.
Advanced Encryption Standard (AES): A symmetric block cipher that can process data in block of minimum 128-bits using cipher keys with lengths of 128, 192 and 256 bits for encryption and decryption of information.
Secret Key: A symmetric cryptographic algorithm uses a single secret key for both encryption and decryption.
Confidentiality: Preserving authorized restrictions on access and disclosure, including means for protecting personal privacy and proprietary information.
Privacy: Keeping information secret from all but those who are authorized to see it. The ability of individual to control the access others have to personal information about them and the expectation of anonymity, fairness and confidentiality.
Encryption: The conversion of the original data (plaintext) into a form called a scrambled data (ciphertext) through the use of a cryptographic algorithm for the purpose of security or privacy.