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Cryptography

Cryptography. The science of writing in secret code. Cryptography is an ancient art - first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription

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Cryptography

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  1. Cryptography The science of writing in secret code

  2. Cryptography is an ancient art - first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription • New forms of cryptography came soon after the widespread development of computer communications The Science of Writing In Secret Code

  3. Crypto is the secure communication in the presence of third parties (adversaries) • Generally: about constructing and analyzing protocols that overcome such adversaries • MAIN GOAL: SECURITY! Secure Communication

  4. Modern crypto intersects disciples of Math, Computer Science, and Electrical Engineering • APPLICATIONS: ATM cards, computer passwords, electronic commerce, etc. Related to various aspects in information security such as data confidentiality, data integrity, authentication DISCIPLINES

  5. Authentication: process of proving one’s identity • Privacy/confidentiality: ensuring that no one can read the message except the intended receiver • Integrity: assuring the intended receiver that the original message has not been altered in any way • Non-repudiation: mechanism to prove that sender really sent the message Specific Security Requirements

  6. Initial unencrypted date is referred to as plaintext • It is then encrypted into ciphertext • Then decrypted into usable plaintext PLAINTEXT PLAINTEXT CIPHERTEXT Cryptographic Schemes

  7. Secret Key Cryptography (SKC) • Public Key Cryptography (PKC) • Hash Functions Types of Cryptography

  8. Crypto

  9. Secret Key Encryption Also known as private key & symmetric key

  10. Secret Key Encryption

  11. Public Key Encryption

  12. Public Key Encryption

  13. Each scheme is optimized for some specific applications • Secret Key Cryptography is suited for encrypting messages as it provides privacy and confidentiality • Public Key Cryptography is ideal for non-repudiation and user authentication • Hash functions ensure data integrity Why Three?

  14. Roman ruler Julius Caesar used a very simple cipher for secret communication Involves the use of a “displacement” concept Caesar cipher is the simplest to solve, since there are only 25 possible combinations Caesar Cipher

  15. Outside wheel: The Alphabet Inner wheel: can be rotated so that any letter on one wheel can be aligned with any letter on the other wheel - The inner wheel becomes the key Caesar Cipher

  16. Caesar Cipher

  17. A lock is only as strong as its weakest link

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