Crytography is Closely related to the disciplines of Cryptology and Cryptanalysis. Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. However, in today's computer-centric world, Cryptography is most often associated with scrambling plaintext into Cipher text (a process called Encryption), then back again (known as decryption). Individuals who practice this field are known as crytographers

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4. What is
&
How it works
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Closely related to the disciplines of Cryptology and Cryptanalysis.
Cryptography includes techniques such as microdots, merging words with images,
and other ways to hide information in storage or transit.
However, in today's computer-centric world,
Cryptography is most often associated with scrambling plaintext
into Cipher text (a process called Encryption), then back again (known as decryption).
Individuals who practice this field are known as
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6. Popular Methods of Securing
Computer Information
Symmetric Cryptography
Asymmetric Cryptography
Elliptic Curve Cryptography
Quantum Cryptography
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7. It includes methods of encryption
that are best suited for processing large streams of data.
It is distinguished the use of a single key for encrypting and
decrypting messages by the sender and receiver.
This type of cryptography is categorized by the use of stream or block
ciphers
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It is also called public key cryptography, encryption methods
are best used for key exchange and user authentication. This
type of cryptography is commonly used in digital signatures. It
is distinguished by the use of a private and public key that are
created with one-way functions using multiplication and
exponentiation. One key is public and published in a public
directory while the private key is only known by the receiver
of the message.

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Data that can be read and understood without any special
measures is called plaintext or cleartext. The method of
disguising plaintext in such a way as to hide its substance is
called encryption. Encrypting plaintext results in unreadable
gibberish called ciphertext. You use encryption to ensure
that information is hidden from anyone for whom it is not
intended, even those who can see the encrypted data. The
process of reverting ciphertext to its original plaintext is
called decryption.

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“Hello World”
Encryption
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Decryption
“Hello World”
(Plaintext) (Plaintext)
Shared Secret Key

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Types of Cryptanalytic Attacks
• ciphertext only
– only know algorithm / ciphertext, statistical, can identify
plaintext
• known plaintext
– know/suspect plaintext & ciphertext to attack cipher
• chosen plaintext
– select plaintext and obtain ciphertext to attack cipher

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Brute Force Search
• always possible to simply try every key
• most basic attack, proportional to key size
• assume either know / recognise plaintext

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Crook #1 changes
his PIN to a number
of his choice
cipher(key,PIN)
PIN is encrypted and
transmitted to bank
Crook #2 eavesdrops
on the wire and learns
ciphertext corresponding
to chosen plaintext PIN
… repeat for any PIN value

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A digital signature is a mathematical scheme for demonstrating
the authenticity of a digital message or
document. A valid digital signature gives a recipient reason to
believe that the message was created by a known sender, that
the sender cannot deny having sent the message
(authentication and non-repudiation), and that the message
was not altered in transit (integrity). Digital signatures are
commonly used for software distribution, financial
transactions, and in other cases where it is important to
detect forgery or tampering.

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18. Final Thoughts on Cryptography
While there are many examples of cryptography,
security of information is never one hundred percent perfect.
Even though more complex encryption methods are always being created,
sophisticated HACKERS can learn to adapt and find a way to crack these systems.
We just need to try and be one step ahead of the game.
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