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Encryption and Key Distribution Methods
- 1. 1 EncryptionEncryption andand Key DistributionKey Distribution MethodsMethods APPLIED DATA COMMUNICATION Tallinn University of Technology Gülçin Yıldırım - Team #12
- 2. 2 What is Encryption?What is Encryption? Encryption is the process of encoding messages or information in such a way that only authorized parties can read it.
- 3. 3 Why Encryption?Why Encryption? Confidentiality Authentication Message Integrity Access and Availability
- 5. 5 Inserting messagesInserting messages Actively insert messages into connection
- 6. 6 ImpersonationImpersonation Can fake (spoof) source address in packet (or any field in packet)
- 7. 7 HijackingHijacking "Take over" ongoing connection by removing sender or receiver by inserting himself in place
- 8. 8 Denial of ServiceDenial of Service Prevent service from being used by others (e.g, by overloading resources)
- 9. 9 Insecure CommunicationInsecure Communication Sender Intended Receiver MITM
- 10. 10 Secure ChannelSecure Channel Sender Intended Receiver MITM
- 11. 11 Encrypted MessageEncrypted Message Sender Intended Receiver MITM
- 13. 13 EncryptionEncryption Generates a ciphertext from a plaintext using an encryption key and an encryption algorithm (cipher) It is a two way process: an encrypted data is expected to be decrypted later.
- 16. 16 Symmetric Key EncryptionSymmetric Key Encryption All communicating parties use the same key Key is used both for encryption and decryption
- 17. 17 Symmetric Key EncryptionSymmetric Key Encryption Faster compared to public key encryption Key needs to be stored securely (only accessed when required) Secure channel required to transfer the key
- 18. 18 Public Key EncryptionPublic Key Encryption Requires two keys: Public Key: used for encryption Private Key: used for decryption All communicating parties exchange their public keys Sender encrypts the plaintext using receiver's public key Receiver decrypts the ciphertext using their own private key
- 19. 19 Public Key EncryptionPublic Key Encryption Slower compared to Symmetric Key Encryption Public key & ciphertext can be sent over an insecure channel More secure because there is no need to share private keys with anyone
- 20. 20 Public Key EncryptionPublic Key Encryption Public Key (share with pink) Private Key (keep it secret) Public Key (share with blue) Private Key (keep it secret)
- 21. 21 Public Key EncryptionPublic Key Encryption
- 22. 22 Logic Behind the KeysLogic Behind the Keys Trying to find a prize behind a series of number of doors
- 23. 23 Public & Symmetric Key MixPublic & Symmetric Key Mix Performance ? Security ? Public key encryption used to exchange keys Symmetric key encryption used to encrypt data
- 24. 24 Encryption AlgorithmsEncryption Algorithms Block Cipher and Stream Cipher
- 25. 25 Encryption AlgorithmsEncryption Algorithms An encryption algorithm is called "cipher" There are two types of ciphers: Block cipher Stream cipher Two concepts are very important for both of them: Prime numbers Entropy for random number generation
- 26. 26 Block CipherBlock Cipher Operates on fixed-size blocks (N bits) and uses fixed-size keys (K bits) 1. Reads N-bits of data from the plaintext 2. Uses the key and applies the encryption algorithm 3. Produces ciphertext in size of N-bits 4. Repeats steps 1-4 until all plaintext is processed
- 27. 27 Block Cipher - AESBlock Cipher - AES One of the most popular block ciphers is the AES algorithm. Some other examples are: DES, Blowfish, RC5, ... AES stands for Advanced Encryption Standard Works on 128 bits (16 bytes) of blocks Uses 128, 192 or 256 bits of keys Operates on a 4x4 matrix of bytes There are four stages in the algorithm: 1. KeyExpansions: Keys are derived from the provided key 2. InitialRound: AddRoundKey 3. Rounds: SubBytes, ShiftRows, MixColumns, AddRoundKey 4. FinalRound: SubBytes, ShiftRows, AddRoundKey
- 28. 28 Block Cipher - AESBlock Cipher - AES
- 29. 29 Stream CipherStream Cipher Operates on variable-size blocks (N bits) and uses random-size keys 1. Generates a random number N 2. Reads N-bits of data from the plaintext 3. Uses the key and applies the encryption algorithm 4. Produces ciphertext in size of N-bits 5. Repeats steps 1-5 until all plaintext is processed A popular stream cipher algorithm is RC4. However, it is replaced by RC5, a block cipher algorithm.
- 30. 30 Key Distribution MethodsKey Distribution Methods The main concern of a key distribution method is how to securely supply keys between all communicating parties There are some important security questions we must consider: Symmetric Key Encryption Is the shared key stored securely? Is it compromised? Is the communication channel secure? Public Key Encryption Am I encrypting for the intended receiver? A key distribution method helps us with those concerns.
- 31. 31 Key Distribution MethodsKey Distribution Methods There are various different key distribution methods for different encryption types: In symmetric key encryption, trusted key distribution center (KDC) is acting as intermediary between parties In public key encryption, public key servers are used for both uploading and downloading public keys One another method is using a public key infrastructure (PKI) to share SSL certificates. A Certificate Authority (CA) provides public keys and also validates SSL certificates
- 32. 32 Use-Case: GPGUse-Case: GPG GPG (GNU Privacy Guard) is a very popular application that uses public key encryption Most commonly used for encryption / decryption of files & email messages Available for many platforms: Linux, Mac OS X, Microsoft Windows, BSD, etc... There are very large key servers to distribute public keys (e.g., MIT PGP Public Key Server)
- 33. 33 Demo - SenderDemo - Sender
- 34. 34 Demo - ReceiverDemo - Receiver