What is cryptography?
Cryptography includes a set of techniques for scrambling or disguising
data. The scrambled data is available only to someone who can restore
the data to its original form. The purpose is to make data unintelligible
to unauthorized persons, but readily decipherable to authorized persons.
Cryptography deals with several processes:
- Enciphering is converting plaintext, which is intelligible, into ciphertext, which is not intelligible. Enciphering is also called encrypting.
- Deciphering is converting ciphertext back into plaintext. Deciphering is also called decrypting.
- Hashing involves using a one-way calculation to condense a long message into a compact bit string, or message digest.
- Generating and verifying digital signatures involves
encrypting a message digest with a private key to create the electronic
equivalent of a handwritten signature. Both a handwritten signature
and a digital signature verify the identity of the signer and cannot
be forged.
Digital signatures also serve to ensure that nothing has altered the signed document since it was signed.
The growth of distributed systems and the increasing use of the Internet have resulted in the need for increased data security. Cryptography provides a strong, economical basis for keeping data confidential and for verifying data integrity. Cryptography is already playing a critical and expanding role in electronic commerce and electronic mail services. Emerging markets that require secure data transmission and the authentication of the sender are already relying on cryptography.