Cryptography is the study of keeping information secure by transforming it into a form which is unintelligible for unintended recipients.It provides secure communications techniques that allow only the sender and intended recipient to be able to understand the content of a message. In cryptography, an original message is called plaintext, and it is transformed into ciphertext by using algorithms or mathematical operations which is not readable for unintended recipients.The term cryptography is derived from the Greek word kryptos, which means hidden. It is closely associated with encryption which is an important part of cryptography.Encryption is the process of turning plaintext into ciphertext. Its opposite is decryption which is the process of turning the cipher text back into plaintext form.Encryption process always consists of algorithm and a key. A key is a piece of information or number which identifies how the algorithm will be applied to the plaintext in order to encrypt it.
Ancient Egyptians were known to use cryptography methods in complex hieroglyphics, and Roman Emperor Julius Caesar is credited with using one of the first modern ciphers which is called as Caesar cipher where letters of a message is shifted by an agreed number (three was a common choice), the recipient of this message would then shift the letters back by the same number and obtain the original message.
There are various applications of cryptography like transmitting financial data safely across the internet,computer passwords, and e- commerce transactions,online banking, keeping military secrets. Overall cryptography can secure data and network. Cryptography techniques and methods are able to:
- Keep the contents of data confidential
- Authenticate the identity of a message's sender and receiver
- Ensure the integrity of the data, showing that it hasn't been altered
- Demonstrate that the supposed sender really sent this message, a principle known as non-repudiation
Types of cryptography
Mainly there are three types of cryptography symmetric key cryptography, public key cryptography, and hash functions.
Symmetric-key Cryptography: Both the sender and receiver share a single key. The sender uses this key to encrypt plaintext and send the cipher text to the receiver. On the other side the receiver applies the same key to decrypt the message and recover the plain text.
Public-Key Cryptography: This is the most revolutionary concept in the last 300-400 years. Public-Key Cryptography is also called asymmetric key cryptography. In public key cryptography each participant has two keys. One is public, and is sent to anyone the party wishes to communicate with.That's the key used to encrypt messages. But the other key is private, shared with nobody, and it's necessary to decrypt those messages.
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.