[Term of the Day]: Cryptography
Term of the Day
“Cryptography”
Definition — What is Cryptography and what is its purpose?
Cryptography is the practice and study of techniques for securing information and communications through the use of codes so that only those persons for whom the information is intended can understand it and process it. Thus preventing unauthorized access to information. Cryptography is a sub-discipline of cryptology, whose meaning is derived from the Greek words “Kruptós” and “logos” meaning “hidden word”.
Earlier cryptography was effectively synonymous with encryption but modern cryptography is mainly based on mathematical theories and a set of rule-based calculations known as algorithms to convert messages in ways that make it hard to decode it. This is often associated with the process where an ordinary plain text is converted to ciphertext which is the text made such that intended receiver of the text can only decode it and hence this process is known as encryption. The process of conversion of cipher text to plain text is known as decryption.
Modern cryptography concerns with:
Confidentiality - Information can only be accessed by the person for whom it is intended and no other person except him can access it.
Integrity - Information cannot be modified in storage or transition between the sender and intended receiver without any addition to information being detected.
Non-repudiation - The creator/sender of information cannot deny his or her intention to send information at a later stage.
Authentication - The identities of the sender and receiver are confirmed. As well as destination/origin of the information is confirmed.
Cryptography is used in many applications like banking transactions cards, computer passwords, and e-commerce transactions. Three types of cryptographic techniques used in general.
1. Symmetric-key Cryptography: Both the sender and receiver share a single key. The sender uses this key to encrypt the plaintext and send the ciphertext to the receiver. On the other side, the receiver applies the same key to decrypt the message and recover the plain text.
2. Hash Functions: No key is used in this algorithm. A fixed-length hash value is computed as per the plain text that makes it impossible for the contents of the plain text to be recovered. Hash functions are also used by many operating systems to encrypt passwords.
3. Public-Key Cryptography: This is the most revolutionary concept in the last 300-400 years. In Public-Key Cryptography two related keys (public and private key) are used. The public key may be freely distributed, while its paired private key, remains a secret. The public key is used for encryption and for decryption private key is used.