Encryption and decryption in public key cryptography

Encryption: The process of changing the plaintext into the ciphertext is referred to as encryption. The encryption process consists of an algorithm and a key. The key is a value independent of the plaintext. The security of conventional encryption depends on the major two factors: The Encryption algorithm Secrecy of the key Once the ciphertext is produced, it may be transmitted.

The Encryption algorithm will produce a different output depending on the specific key being used at the time. Changing the key changes the output of the algorithm. Once the ciphertext is produced, it may be transmitted. Upon reception, the ciphertext can be transformed back to the original plaintext by using a decryption algorithm and the same key that was used for encryption. Decryption: The process of changing the ciphertext to the plaintext that process is known as decryption.

Public Key Encryption : Asymmetric is a form of Cryptosystem in which encryption and decryption are performed using different keys-Public key known to everyone and Private key Secret key. This is known as Public Key Encryption. Image encryption and decryption in public key cryptography based on MR Abstract: In the past decade, image encryption is given much attention in research of information security and a lot of image encryption algorithms have been introduced.

Due to some intrinsic features of images like bulk data capacity and high data redundancy, the encryption of image is different from that of text; therefore it is difficult to handle them by traditional encryption methods. In the proposed work, a new image encryption algorithm based on Magic Rectangle MR is being applied.

To begin with, the plain-image is converted into blocks of single bytes and then the block is replaced as the value of MR. An example of generating RSA Key pair is given below. Practically, these values are very high. Once the key pair has been generated, the process of encryption and decryption are relatively straightforward and computationally easy. Interestingly, RSA does not directly operate on strings of bits as in case of symmetric key encryption.

It operates on numbers modulo n. Hence, it is necessary to represent the plaintext as a series of numbers less than n. To encrypt the first plaintext P, which is a number modulo n.

In other words, the ciphertext C is equal to the plaintext P multiplied by itself e times and then reduced modulo n. This means that C is also a number less than n. The decryption process for RSA is also very straightforward.

Suppose that the receiver of public-key pair n, e has received a ciphertext C. Receiver raises C to the power of his private key d. The result modulo n will be the plaintext P. The security of RSA depends on the strengths of two separate functions. The RSA cryptosystem is most popular public-key cryptosystem strength of which is based on the practical difficulty of factoring the very large numbers.

If either of these two functions are proved non one-way, then RSA will be broken. In fact, if a technique for factoring efficiently is developed then RSA will no longer be safe. Along with RSA, there are other public-key cryptosystems proposed. Many of them are based on different versions of the Discrete Logarithm Problem. It derives the strength from the assumption that the discrete logarithms cannot be found in practical time frame for a given number, while the inverse operation of the power can be computed efficiently.

Let us go through a simple version of ElGamal that works with numbers modulo p. In the case of elliptic curve variants, it is based on quite different number systems. It is a generator of the multiplicative group of integers modulo p.

Choosing the private key.