Page 130 - DCAP309_INFORMATION_SECURITY_AND_PRIVACY

Information Security and Privacy

Notes  With symmetric key cryptography, a single key is used for both encryption and decryption.
The sender uses the key (or some set of rules) to encrypt the plaintext and sends the
ciphertext to the receiver.
 Public-key cryptography, also known as asymmetric cryptography, is a form of
cryptography in which a user has a pair of cryptographic keys — a public key and a private
key.
 Hash algorithms are typically used to provide a digital fingerprint of a file’s contents
often used to ensure that the file has not been altered by an intruder or virus.
 Kerberos employs a client/server architecture and provides user-to-server authentication
rather than host-to-host authentication.

8.7 Keywords

Block Cipher: It is one kind of encryption scheme which encrypts one block of data at a time
using the same key on each block.
Cipher Block Chaining: It is one kind of encryption mode which adds a feedback mechanism to
the encryption scheme.
Cipher Feedback: It is one kind of encryption mode which allows data to be encrypted in units
smaller than the block size, which might be useful in some applications such as encrypting
interactive terminal input.
Decryption: It is the reverse process of converting encoded data to its original un-encoded form,
plaintext.
Digital Certificate: It is trusted ID card in electronic form that binds a website’s public encryption
key to their identity for purposes of public trust.
Electronic Codebook: It is one kind of encryption mode where the shared key is used to encrypt
the plaintext block to form a ciphertext block.
Encryption: It is a process of coding information which could either be a file or mail message in
into cipher text a form unreadable without a decoding key in order to prevent anyone except the
intended recipient from reading that data.
Hash Function: It is one-way encryption that uses no key.
Output Feedback: It is one kind of encryption mode which prevents the same plaintext block
from generating the same ciphertext block by using an internal feedback mechanism that is
independent of both the plaintext and ciphertext bitstreams.
Public-key Cryptography: It is a form of cryptography in which a user has a pair of cryptographic
keys—a public key and a private key; the private key is kept secret, while the public key may be
widely distributed.
Stream Cipher: It is one kind of encryption scheme where the plaintext block is encrypted to the
different ciphertext.
Symmetric Key Cryptography: It is one kind of encryption process where a single key is used for
both encryption and decryption.
8.8 Review Questions

1. What is cryptography? Elucidate various applications of cryptography.
2. Illustrate the process of symmetric key cryptography.

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