Learn about basic terms in Cryptography

There are many terms regarding cryptography. They can be briefly listed as below:
1. Encryption
2. Decryption
3. Encode / Decode
4. Encipher / Decipher
5. Cryptosystem
6. Plaintext
7. Ciphertext
8. Key
9. Keyless cipher
10. Cryptography
11. Cryptanalyst
12. Cryptographer
13. Cryptology
14. Cryptanalysis
15. Substitution encryption / Transposition encryption
16. Public key / Private Key.

ENCRYPTION:
Encryption is the formal names for the scrambling process. We take data in their normal, unscrambled state, called cleartext, and transform them so that they are unintelligible to the outside observer; the transformed data are called encrypted text.
Thus Encryption is the process of encoding message so that its meaning is not obvious. Encryption is the group term that covers both encoding and enciphering.

DECRYPTION:
Decryption is the reverse process, transforming an encrypted message back into its normal original form

ENCODE / DECODE:
Encoding is the process of translating entire words or phrases to other words or phrases.
Decoding is the reverse process of translating the encoded words or phrases into the original words or phrases.

ENCIPHER / DECIPHER:
Enciphering is translating letters or symbols individually into another form. Deciphering is as usual the reverse process of enciphering.
Alternatively the terms encode and decode or encipher and decipher are used instead of encrypt and decrypt. That is, we encode, encrypt, or encipher the original message to hide its meaning. Then we decode, decrypt, or decipher it to reveal the original message.

CRYPTOSYSTEM:
A system for encryption and decryption is called as a cryptosystem.

PLAINTEXT & CIPHERTEXT:
The original form of a message is known as plaintext, and the encrypted text is called ciphertext.

KEY:
The cryptosystem involves a set of rules for how to encrypt the plaintext and how to decrypt the ciphertext. The encryption and the decryption rules, called algorithms, often use a device called a key denoted by K, so that the resulting ciphertext depends on the original plaintext message, the algorithms, and the key valve. The dependence is written as
C = E (K, P).
Essentially, e is the set of encryption algorithms and the key k selects one specific algorithm from the set.

KEYLESS CIPHER:
An encryption scheme that does not require the use of a key is called a keyless cipher.

CRYPTOGRAPHY:
Cryptography means hidden writing, and it refers to the practice of using encryption to conceal text. A definition depending on the mathematical influence into cryptography gives a definition relating to mathematics and cryptography.
“Cryptography is a collection of mathematical techniques for protecting information. Using cryptography one can transform written words and other kinds of messages so that they are unintelligible to anyone who does not possess a specific mathematical key necessary to unlock the message. The process of using cryptography to scramble a message is called encryption. The process of unscrambling the message by the use of appropriate key is called decryption.”

CRYPTANALYST:
A cryptanalyst studies encryption and encrypted messages, hoping to find the hidden meanings. A cryptanalyst chore is to break an encryption.

CRYPTOGRAPHER:
A cryptographer and a cryptanalyst attempt to translate coded material back to its original form. Normally a cryptographer works on behalf of a legitimate sender or receiver, whereas a cryptanalyst works on behalf of an unauthorized interceptor.

CRYPTOLOGY:
Cryptology is the research into and study of encryption and decryption; it includes both cryptography and cryptanalysis.

CRYPTANALYSIS:
Analyzing a cryptographic code to deduce the original meaning of the code or just to identify the pattern of encryption used is called as cryptanalysis.

SUBSITUTION CIPHER:
Substitution cipher uses a correspondence table with which to substitute a character or symbol for each character of the original message. This technique is also called as monoalphabetic cipher or simple substitution. A substitution is an acceptable way of encrypting text.
E.g.: Caesar cipher, Vernam cipher etc.

TRANSPOSITION CIPHER:
A transposition is an encryption in which the letters of the message are rearranged. With transposition, the cryptography aims for diffusion, widely spreading the information from message or the key across the ciphertext. Transpositions try to break established patterns. Because a transposition is a rearrangement of the symbols of a message, it is also called as a permutation.
E.g.: columnar transposition, Digrams, Trigrams etc.


PUBLIC KEY / PRIVATE KEY:
This pair of keys is used for symmetric and asymmetric encryptions. They should be selected in the way that if one is used for encryption, then the other is used for decryption. Symmetric encryption is called as a secret key encryption or a private key encryption. In this type the sender and the receiver both share the same type of key used for encryption and decryption.
In public key or asymmetric encryption each user has two keys: public key and a private key. The user may publish the public key freely because each key does only half of the encryption and decryption process. The keys operate as inverses, meaning that one key undoes the encryption provided by the other key.