Images unduly assist digital communication in this aeon of multimedia. During times a person transmits confidential images over a flabby communication network, sheer protection is an accost contention to preserve the privacy of images. Encryption is one of the practice to clutch the reticence of images. Image encryption contributes a preeminent bite to charter security for secure sight data communication over the internet. Our work illustrates a survey on image encryption in different domains providing concise exordium to cryptography, moreover, furnishing the review of sundry image encryption techniques.
TopPreliminaries
Cryptography is the art or science encompassing the principles and methods of transforming an intelligible message into one that is unintelligible, and then retransforming that message back to its original form.
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Plaintext: Plaintext is the original intelligible message.
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Ciphertext: Ciphertext is the transformed message.
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Encryption: Encryption is the process (algorithm) for transforming a plaintext into a ciphertext.
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Decryption: Decryption is the reverse process of encryption, i.e. transforming the ciphertext back to plaintext.
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Key: Key is the most important data used by encryption algorithms, known to the both authorized parties. Encryption mechanisms relies on the key. Encryption algorithms are available for all, so, attacker’s objective is to achieve the key.
Basic cryptography process for a text message at its simplest form can be described as:
Plaintext P=[P1, P2, …, PX] of length X, where X belongs to finite alphabet set. The key K=[K1, K2, …, KY] of length Y. Ciphertext C=[C1, C2, …, CZ] of length Z. With message P and key K the encryption algorithm creates the ciphertext C=EK(P). The plaintext can be achieved by P=DK(C). D being the decryption algorithm.
A cryptosystem thus can be formulated mathematically as a five tuple (P, C, K, E, D) where the following should satisfy:
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P is a finite set of possible plaintext.
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C is a finite set of possible ciphertext.
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K, the key space, is the finite set of possible keys.
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E is encryption rule, and, D is decryption rule.
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∀k∈K, ∃ek∈E, ∃dk∈D