Introduction•If you have the best firewall, very tight security policies, hardened systems, virus scanners, intrusion-detection software, antispyware, and every other computer security angle covered but send your data in raw, plain text, then you simply are not secure.•There is the need to have messages changed in such a way that the message cannot be easily read by an enemy, but they can be easily decoded by the intended recipient•That's where cryptography / encryption is necessary
Cryptography Vs. EncryptionCryptography•The science of coding and decoding messages so as to keep these messages secure.•It is a discipline or techniques employed in protecting integrity or secrecy of electronic messages by converting them into unreadable form. Only the use of a secret key can convert the cipher text back into human readable form. Cryptography software and/or hardware devices use mathematical formulas (algorithms) to change text from one form to another. The aim of cryptography is not to hide the existence of a message, but rather to hide its meaning.Encryption•Encryptionis the process of encoding messages or information in such a way that only authorized parties can read. Encryption protects against passive attack (eavesdropping).
Secure Communication ModelAlice BobOscarEncryptSecret KeyxyDecryptKKSecret ChannelK
Terminology•Plaintext: This is the original message or data that is fed into the algorithm as input.•Encryption algorithm: The encryption algorithm performs various substitutions and transformations on the plaintext.•Secret key: The secret key is also input to the algorithm. The exact substitutions and transformations performed by the algorithm depend on the key.•Ciphertext: This is the scrambled message produced as output. It depends on the plaintext and the secret key. For a given message, two different keys will produce two different ciphertexts.•Decryption algorithm: This is essentially the encryption algorithm run in reverse. It takes the ciphertext and the same secret key and produces the original plaintext.•Cryptanalysis-The process of attempting to discover the plaintext or key is known as cryptanalysis . The strategy used by the cryptanalyst depends on the nature of the encryption scheme and the information available to the cryptanalyst
Types of Attacks on Encrypted Messages
Types of Cryptography•There are two basic types of cryptography: •symmetric and asymmetric. •Symmetric means the same key is used to encrypt the message and to decrypt the message. •With asymmetric cryptography, a different key is used to encrypt the message than is used to decrypt the message
Symmetric key Encryption•Symmetric key encryption means that the same key is used to both encrypt and decrypt a message. This is also referred to as Single-Key (Symmetric) Encryption.
You've reached the end of your free preview.
Want to read all 54 pages?
- Fall '18
- Dr. Yarkson Gustave