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Cryptography is the science of informationsecurity.

The word is derived from theGreek kryptos , meaning hidden.

Cryptography includes techniques such asmicrodots, merging words with images, and

other ways to hide information in storage or transit.

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Confidentiality :- the information cannot be understoodby anyone for whom it was unintended.

Integrity :-the information cannot be altered in storageor transit between sender and intended receiver withoutthe alteration being detected.

Authentication :-the sender and receiver can confirmeach others identity and the origin/destination of theinformation.

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Overview of Cryptography & ItsApplications

People want and need privacy and security whilecommunicating.

In the past, cryptography is heavily used for militaryapplications to keep sensitive information secret from

enemies (adversaries). Nowadays, with the technological progress as our

dependency on electronic systems has increased we needmore sophisticated techniques.

Cryptography provides most of the methods and techniquesfor a secure communication

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Cryptography components

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Encryption It is a process of changing or converting normal text or data information intogibberish text.

Decryption It is a process of changing or converting gibberish text back to correct

message or data by using encryption method.

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Cryptology : All-inclusive term used for the study of securecommunication over non-secure channels.

Cryptography : The process of designing systems to realizesecure communications over non-secure channels.

Cryptoanalysis : The discipline of breaking the cryptographicsystems.

Coding Theory : Deals with representing the informationusing codes. It covers compression, secrecy, and error correction.

Terminology

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The Aspects of Cryptography

Modern cryptography heavily depends on mathematics andthe usage of digital systems.

It is a inter-disciplinary study of basically three fields:Mathematics

Computer ScienceElectrical Engineering

Without having a complete understanding of crypto analysis(or cryptoanalytic techniques) it is impossible to designgood (secure, unbreakable) cryptographic systems.

It makes use of other disciplines such as error-correcting codescompression.

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Categories of cryptography

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A single common encryption key is used toencode and decode messages.

Both sender and receiver must know thecommon key.

The common key need to be exchangedbefore hand by some other secure method.

Symmetric encryption is simple and fast.

But - key management is impractical withlarge number of senders and receivers.

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Symmetric-key cryptography

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Asymmetric system under, which two differentkeys are used to encrypt and decrypt themessage or received data packet.

On public key is used to encrypt the data or message and the private key on receiving endis used to decrypt the message or datapacket.

Each user has a Public key and acorresponding Private (secret) key

Asymmetric-key cryptography

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Asymmetric-key cryptography

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Keys used in cryptography

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public-key cryptography Increased securityand convenience.

public-key cryptography is best suited for anopen multi-user environment.

Symmetric encryption is simple and fast.

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