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# Cryptography

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### Cryptography

1. 1. By: Sagar Janagonda Cryptography
2. 2. Contents  What is Cryptography...?  Security Requirements  Encryption & Decryption  Types of Cryptography  What is KEY…?  Advantages  Disadvantages  Conclusion
3. 3. Definition Cryptography is the science of information security. Derived from the Greek word “KRYPTOS”. Writing in secret code and is an ancient art. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, particularly the Internet.
4. 4. Some specific security requirements  Authentication: The process of proving one's identity.  Privacy: Ensuring that no one can read the message except the intended receiver.  Integrity: Assuring the receiver that the received message has not been altered in any way from the original.  Non-repudiation: A mechanism to prove that the sender really sent this message.
5. 5. Encryption It is the transformation of data into some unreadable form. Its purpose is to keep the information hidden from anyone for whom it is not intended.
6. 6. Decryption It is the reverse of encryption. It is transformation of encrypted data back into some clear form.
7. 7. Types of Cryptography  Secret Key Cryptography: Uses a single key for both encryption and decryption.  Public Key Cryptography: Uses one key for encryption and another for decryption.  Hash Functions: Uses a mathematical transformation to encrypt information.
8. 8. What is Key….? In cryptographic systems, the term key refers to a numerical value used by an algorithm to alter information, making that information secure and visible only to individuals who have the corresponding key to recover the information.
9. 9. The art of protecting information by transforming it into an unreadable format, called cipher text.
10. 10. Secret Key Cryptography It is also known as symmetric key cryptography. Messages are encrypted by the sender using the key and decrypted by the receiver using the same key. Suitable for communicating with only a limited number of people. Eg: DES , IDEA
11. 11. Public Key Cryptography Uses a pair of keys for encryption and decryption. With public key cryptography, keys work in pairs of matched public and private keys. The public key can be freely distributed without compromising the private key, which must be kept secret by its owner. Because these keys work only as a pair, encryption initiated with the public key can be decrypted only with the corresponding private key. Eg: Diffie-Hellman RSA(Ronald Rivest, Adi Shamir, and Leonard Adleman) Encrypted Document DocumentDocument Public Key Private Key Encrypted Document
12. 12. Hash Functions Also called message digests and one-way encryption, are algorithms that use no key. A fixed-length hash value is computed based upon the plaintext that makes it impossible for either the contents or length of the plaintext to be recovered. Typically used to provide a digital fingerprint of a file's contents. Provide a measure of the integrity of a file.
13. 13. Different Hash Algorithms  Message Digest (MD) algorithms: Produce a 128-bit hash value.  Secure Hash Algorithm (SHA): Produces a 160-bit hash value.  RIPEMD: RACE Integrity Primitives Evaluation. 32-bit  HAVAL: Hash of Variable Length hash values that are 128, 160, 192, 224, or 256 bits in length.  Whirlpool: Operates on messages less than 2256 bits in length, and produces a message digest of 512 bits. Tiger: Designed to be secure, run efficiently on 64-bit processors.
14. 14. Signed Messages Message + Signature Hash Decrypt Signature With Sender’s Public Key SIGN hash With Sender’s Private key Message + signature COMPARE Calculated HashMessage Sender Receiver Hash Sent thru’ Internet if OK Signatures verified
15. 15. Advantages  It hides the message and your privacy is safe.  No one would be able to know what it says unless there's a key to the code.  You can write what ever you want and how ever you want (any theme any symbol for the code) to keep your code a secret.  You are able to use Cryptography during lessons without the teacher knowing.
16. 16. Disadvantages  Takes a long time to figure out the code.  It takes long to create the code.  If you were to send a code to another person in the past, it will take long to get to that person.  Overall it’s a long process.
17. 17. Conclusion As the Internet and other forms of electronic communication become more prevalent, electronic security is becoming increasingly important. Cryptography is used to protect e-mail messages, credit card information, and corporate data. One of the most popular cryptography systems used on the Internet is Pretty Good Privacy because it's effective and free.
18. 18. Thank you…!