Lecturer : Kartik Krishnan Lectures 22 - 24 Symmetric Key cryptosystem
نویسنده
چکیده
Symmetric encryption, also referred to as conventional encryption or single key encryption was the only type of encryption in use prior to the development of public-key encryption in 1976. The symmetric encryption scheme has five ingredients (see Figure 1): 1. Plaintext: This is the original intelligible message or data that is fed to the algorithm as input. 2. Encryption algorithm: The encryption algorithm performs various substitutions and permutations on the plaintext (see the examples of the substitution and permutation ciphers in Lecture 8). 3. Secret Key: The secret key is also input to the encryption algorithm. The exact substitutions and permutations performed depend on the key used, and the algorithm will produce a different output depending on the specific key being used at the time. 4. Ciphertext: This is the scrambled message produced as output. It depends on the plaintext and the key. The ciphertext is an apparently random stream of data, as it stands, is unintelligible. 5. Decryption Algorithm: This is essentially the encryption algorithm run in reverse. It takes the ciphertext and the secret key and produces the original plaintext. There are two requirements for a symmetric key cryptosystem 1. We assume it is impractical to decrypt a message on the basis of the ciphertext plus knowledge of the encryption/decryption algorithm. In other words, we do not need to keep the algorithm secret; we need to keep only the key secret. 2. Sender and the receiver must have obtained copies of the secret key in a secure fashion and must keep the key secure. If someone can discover the key and knows the algorithm, all communications using this key is readable. We will describe how we can use a public-key cryptosystem for a secure key exchange later in this lecture.
منابع مشابه
Chaos Based Cryptography
This paper shall discuss the design of a Chaos based symmetric key cryptosystem. The structure of two contemporary symmetric key encryption schemes using the Logistic map is discussed and their performance is evaluated based on a battery of tests and some qualitative measures. It is deduced that one scheme performs far better than the other. It is then experimentally shown that the performance ...
متن کاملHardware Implementation of Dynamic S-BOX to Use in AES Cryptosystem
One of the major cipher symmetric algorithms is AES. Its main feature is to use S-BOX step, which is the only non-linear part of this standard possessing fixed structure. During the previous studies, it was shown that AES standard security was increased by changing the design concepts of S-BOX and production of dynamic S-BOX. In this paper, a change of AES standard security is studied by produc...
متن کاملImproving the Rao-Nam secret key cryptosystem using regular EDF-QC-LDPC codes
This paper proposes an efficient joint secret key encryption-channel coding cryptosystem, based on regular Extended Difference Family Quasi-Cyclic Low-Density Parity-Check codes. The key length of the proposed cryptosystem decreases up to 85 percent using a new efficient compression algorithm. Cryptanalytic methods show that the improved cryptosystem has a significant security advantage over Ra...
متن کاملHybrid encryption/decryption technique using new public key and symmetric key algorithm
This research study proposes Hybrid Encryption System using new public key algorithm and private key algorithm. A hybrid cryptosystem is one which combines the convenience of a public-key cryptosystem with the efficiency of a symmetrickey cryptosystem. Here, we propose a provably two way secured data encryption system, which addresses the concerns of user’s privacy, authentication and accuracy....
متن کامل