3. • Cryptography is the science of
information security.
• The word is derived from the
Greek kryptos, meaning hidden.
• Cryptography includes techniques
such as microdots, merging words
with images, and other ways to
hide information in storage or
transit.
4.
5. • Confidentiality:- the information cannot be understood
by anyone for whom it was unintended.
• Integrity :-the information cannot be altered in storage
or transit between sender and intended receiver without
the alteration being detected.
• Authentication :-the sender and receiver can confirm
each others identity and the origin/destination of the
information.
6. Overview of Cryptography & Its
Applications
• People wants and needs privacy and security while
communicating.
• In the past, cryptography is heavily used for military
applications to keep sensitive information secret from
enemies (adversaries).
• Nowadays, with the technologic progress as our
dependency on electronic systems has increased we need
more sophisticated techniques.
• Cryptography provides most of the methods and techniques
for a secure communication
8. • Encryption – It is a process of changing or
converting normal text or data information into
gibberish text.
• Decryption – It is a process of changing or
converting gibberish text back to correct
message or data by using encryption method.
9. Terminology
Cryptology : All-inclusive term used for the study of secure
communication over non-secure channels.
Cryptography : The process of designing systems to realize
secure communications over non-secure channels.
Cryptoanalysis : The discipline of breaking the cryptographic
systems.
Coding Theory : Deals with representing the information
using codes. It covers compression, secrecy, and
error correction.
10. The Aspects of Cryptography
• Modern cryptography heavily depends on mathematics and
the usage of digital systems.
• It is a inter-disciplinary study of basically three fields:
Mathematics
Computer Science
Electrical Engineering
• Without having a complete understanding of crypto analysis
(or cryptoanalytic techniques) it is impossible to design
good (secure, unbreakable) cryptographic systems.
• It makes use of other disciplines such as error-correcting codes
compression.
12. • A single common encryption key is used to
encode and decode messages.
• Both sender and receiver must know the
common key.
• The common key need to be exchanged
before hand by some other secure method.
• Symmetric encryption is simple and fast.
• But - key management is impractical with
large number of senders and receivers.
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14. Asymmetric-key cryptography
• Asymmetric system under, which two different
keys are used to encrypt and decrypt the
message or received data packet.
• On public key is used to encrypt the data or
message and the private key on receiving end
is used to decrypt the message or data
packet.
• Each user has a Public key and a
corresponding Private (secret) key
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17. • Sender”sign” messages by means of his
private secret key.
• Recipient verify the senders signature by
means of the senders public key.
• The senders identity is certified by means of
a”Certificate” which is digitally signed by a
trusted third party.
18. • public-key cryptography Increased security
and convenience.
• public-key cryptography is best suited for an
open multi-user environment.
• Symmetric encryption is simple and fast.
19. • cryptography = physics + Information
theory
• Information is physical.
• Information gain implies disturbances.
