Cryptography
Cryptography:
One of the most important things in our daily lives is to communicate with each other.We communicate to gain knowledge or share our knowledge. Some times the information we need to share the information secretly through a medium of communication, for example through telegram.
Cryptography is defined as encoding the original information in some form so that the third person cannot know the details when a message is to be send between two people.
Caeser Shift Cipher: Here the alphabets are shifted by a desired number, after that they are mapped to their respective values.The original message is encoded based on the values of the alphabets.
Steganography: Here after encoding the original message ,the sender also wants to make sure that the encoded message is not visible to the third person.Example : watermarks
Goals of cryptograhy:
Confidentiality: Keeps the information secure from unauthorised person.
Data Integrity: If any one makes changes in the encoded code,at the end the receiver should be able to retrieve the original information.
Authentication:
Non-repudiation: Once the message is set to be send to a particular person,it need to be accepted abd cannot be rejected.
Types of Cryptosystems:
Symmetric Key Encryption: Sender and Reciever has same to encrypt and decrypt
Asymmetric Key Encryption: Sender and Reciever donot have the same key.
Attacks are classified as follows:
Passive: Accessing the information the transmission medium without having the authentication right.
Active : Changing the information in some way by conducting some process on the information.
Earlier Cryptographic Systems:
Caesar Cipher: Shifting the letters.
Simple Substitution Cipher:
Monoalphabetic Cipher: Substitution cipher in which for a given key, the cipher alphabet for each plain alphabet is fixed throughout the encryption process
Polyalphabetic Cipher: Substitution cipher in which the cipher alphabet for the plain alphabet may be different at different places during the encryption process.
Modern Symmetric Key Encryption:
Block Ciphers
Stream Ciphers
One of the most important things in our daily lives is to communicate with each other.We communicate to gain knowledge or share our knowledge. Some times the information we need to share the information secretly through a medium of communication, for example through telegram.
Cryptography is defined as encoding the original information in some form so that the third person cannot know the details when a message is to be send between two people.
Caeser Shift Cipher: Here the alphabets are shifted by a desired number, after that they are mapped to their respective values.The original message is encoded based on the values of the alphabets.
Steganography: Here after encoding the original message ,the sender also wants to make sure that the encoded message is not visible to the third person.Example : watermarks
Goals of cryptograhy:
Confidentiality: Keeps the information secure from unauthorised person.
Data Integrity: If any one makes changes in the encoded code,at the end the receiver should be able to retrieve the original information.
Authentication:
Non-repudiation: Once the message is set to be send to a particular person,it need to be accepted abd cannot be rejected.
Types of Cryptosystems:
Symmetric Key Encryption: Sender and Reciever has same to encrypt and decrypt
Asymmetric Key Encryption: Sender and Reciever donot have the same key.
Attacks are classified as follows:
Passive: Accessing the information the transmission medium without having the authentication right.
Active : Changing the information in some way by conducting some process on the information.
Earlier Cryptographic Systems:
Caesar Cipher: Shifting the letters.
Simple Substitution Cipher:
Monoalphabetic Cipher: Substitution cipher in which for a given key, the cipher alphabet for each plain alphabet is fixed throughout the encryption process
Polyalphabetic Cipher: Substitution cipher in which the cipher alphabet for the plain alphabet may be different at different places during the encryption process.
Modern Symmetric Key Encryption:
Block Ciphers
Stream Ciphers
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