Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties called adversaries. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages; various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation are central to modern cryptography.

History

Cryptography prior to the modern age was effectively synonymous with encryption, the conversion of information from a readable state to apparent nonsense. The originator of an encrypted message shared the decoding technique needed to recover the original information only with intended recipients, thereby precluding unwanted persons from doing the same.

Modern Cryptography

Modern cryptography is heavily based on mathematical theory and computer science practice; cryptographic algorithms are designed around computational hardness assumptions, making such algorithms hard to break in practice by any adversary. It is theoretically possible to break such a system, but it is infeasible to do so by any known practical means.

Cryptographic Algorithms

Cryptographic algorithms are divided into two categories: symmetric key algorithms (Private-key cryptography) and public key algorithms. In a symmetric key algorithm, the sender and receiver must have a shared key set up in advance and kept secret from all other parties; the sender uses this key for encryption, and the receiver uses the same key for decryption. In a public key algorithm, there are two keys: a public key, which is known to all, and a private key, which is known only to the recipient of the messages.

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key. Cryptanalysis is also referred to as codebreaking or cracking the code.

Cryptography in the World

Cryptography is used in many applications like banking transactions cards, computer passwords, and e-commerce transactions.

See Also

• Encryption
• Decryption
• Symmetric key algorithm
• Public key algorithm
• Cryptanalysis

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