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Cryptography simple report
[attachment=15951]
What is Cryptography?
This is the art of
keeping messages
secret
Secret Key Cryptography-
Follows SYMMETRIC
ALGORITHMS.
Single key used to
encrypt and decrypt.
Key must be known
by both parties.
Public Key Cryptography-
Follows ASYMMETRIC
ALGORITHMS.
Each entity has 2 keys:
private key (a secret)
public key (well known)
Using Keys
Private keys are used for
decrypting.
Public keys are used for
encrypting.
encryption
plaintext ----------------- ciphertext
public key
decryption
Ciphertext ----------------- plaintext
private key
Message Digest
Also known as “hash function” or “one-way
transformation”.
Transforms a message
of any length and
computes a fixed
length string.
Need of Digest-
Alisha could just encrypt her name, and then
Bijay could decrypt it with IMAGE
Posts: 6,566
Threads: 1,107
Joined: Jul 2011
Posts: 6,566
Threads: 1,107
Joined: Jul 2011
Cryptography simple report
[attachment=16985]
Main sources
Network Security Essential / Stallings
Applied Cryptography / Schneier
Handbook of Applied Cryptography / Menezes, van
Oorschot, Vanstone
Innovative Cryptography, N. Moldovyan , A.Moldovyan
Modern Cryptography: Theory and Practice, Wenbo Mao
Steganography
.Steganography
Steganos = “covered” in Greek, Graphein = “to write”
.Being able to communicate secretly has always been
considered an advantage
Secret messages were often not written down, but rather
memorized by sworn messengers
.Or hidden
Demaratus, a Greek immigrant to Persia, reveals Persia’s
intention to attack Athens. Writes the secret message on a
tablet, and covers it with wax.
Histaiaeus encourages Aristagoras of Miletus to revolt
against the Persian King. Writes message on shaved head
of the messenger, and sends him after his hair grew
Chinese wrote on silk, turned into wax-covered ball that was
swallowed by the messenger
The classical cryptographic task is to provide for
a reversible transformation of an understandable
plaintext (original text) to a seemingly random
character sequence called a ciphertext or a
cryptogram.
The security of modern cryptosystems is not
based on the secrecy of the algorithm, but on
the secrecy of a relatively small amount of
information, called a secret key.
Applications of Cryptography
Protection against unauthorized reading (or providing information privacy)
Protection against creating false messages (both intentional and
unpremeditated)
Valid user authentication
Information integrity control
Information authentication
Digital signatures
Computerized secret voting
Digital cash
Computerized coin-tossing
Protection against the repudiation of the receipt of a message
Simultaneous contract signing
Protection against document forgery
