Unit4 cry

Introduction to Cryptography
Dr Mohammad Zunnun Khan

• Cryptography is a method of protecting information and
communications through the use of codes so that only those for
whom the information is intended can read and process it.
• The pre-fix "crypt" means "hidden" or "vault" and the suffix "graphy"
stands for "writing."

• In computer science-
• It refers to secure information and communication techniques
derived from mathematical concepts and a set of rule-based
calculations called algorithms to transform messages in ways that are
hard to decipher(decode).

• Modern cryptography concerns itself with the following four
objectives:
• 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
• Non-repudiation: the creator/sender of the information cannot deny at a later
stage his or her intentions in the creation or transmission of the information
• Authentication: the sender and receiver can confirm each other's identity and
the origin/destination of the information

Types of cryptography
• Single-key or symmetric-key encryption algorithms create a fixed
length of bits known as a block cipher with a secret key that the
creator/sender uses to encipher data (encryption) and the receiver
uses to decipher it.
• Types of symmetric-key cryptography include the Advanced
Encryption Standard (AES), a specification established in November
2001 by the National Institute of Standards and Technology as a
Federal Information Processing Standard (FIPS 197), to protect
sensitive information.
• The standard is mandated by the U.S. government and widely used in
the private sector.

• Public-key or asymmetric-key encryption algorithms use a pair of
keys, a public key associated with the creator/sender for encrypting
messages and a private key that only the originator knows (unless it
is exposed or they decide to share it) for decrypting that information.
• The types of public-key cryptography include RSA, used widely on the
internet; Elliptic Curve Digital Signature Algorithm (ECDSA) used by
Bitcoin; Digital Signature Algorithm (DSA) adopted as a Federal
Information Processing Standard for digital signatures by NIST in FIPS
186-4; and Diffie-Hellman key exchange.

Unit4 cry

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