These random keys are generated based on specific information from some predefined sources. We randomly generate a secret key and encrypt data using that key.įor example, in SSL communications, we generate a very large random number and utilize that to encrypt the communication. Modern cryptosystems rely heavily on randomly generated keys. Randomness is a measure of uncertainty in an outcome and thus is applied to the concept of information entropy. It states that the matter should be at a uniform temperature. In other words, it is the expected value of the information contained in each message. In cosmology, entropy is described as a hypothetical tendency of the universe to attain a state of maximum homogeneity. In Information Theory, entropy is a measure of unpredictability of information contained in a message. It might just be me, but things seemed a lot clearer when I no longer attempted to impose my preconceived notion of information on the equations. (It is also a measure of information, but, personally, I prefer the uncertainty interpretation.
In other words, an encryption algorithm is said to be entropically secure if it is computationally infeasible for an adversary to extract any information about the plaintext from the corresponding ciphertext. Entropy, in other words, is a measure of uncertainty. So, an attacker can do some statistical analysis on the ciphertext and gain much knowledge on the plaintext.Įntropic security of an encryption scheme is similar to semantic security when the message spaces have highly entropic distribution. They always produce the same ciphertext for a given plaintext and key when we perform the encryption over and over again. Some encryption schemes, such as RSA without encryption padding and many block ciphers used in Electronic Codebook (ECB) mode or block ciphers with a constant initialization vector cannot be called semantically secure. In cryptography, a cryptosystem is said to be semantically secure if it is computationally infeasible for an attacker to extract any knowledge of the plaintext based on the ciphertext and its length. Entropic Security is a security definition which is used to indicate how difficult it is for an attacker to extract meaningful information about the plaintext from the ciphertext when he does not know the secret key. Many a time attackers manage to extract meaningful information about the plaintext message from the ciphertext. But, no modern encryption algorithm is absolutely secure. The purpose is, an adversary should not be able to retrieve the secret plaintext message from the ciphertext, provided he does not know the secret key.
We take a plaintext message and encrypt it using a strong encryption key to generate the ciphertext. We use encryption to keep our sensitive data safe and secure.
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