Known-Plaintext Attack Against a Permutation Based Video

One of the approaches to deliver real-time video encryption is to apply permutations to the bytes within a frame of a fully encoded MPEG stream as presented in [2]. We demonstrate that this particular algorithm is vulnerable to a known-plaintext attack, and hence its use should be carefully considered. We also discuss modifications that can make the algorithm resistant to our attack

A known plaintext attack on the ISAAC keystream generator

Stream ciphers are often used in applications where high speed and low delay are a requirement. The ISAAC keystream generator is a fast software-oriented encryption algorithm. In this papers the security of the ISAAC keystream generator is investigated. Cryptanalytic algorithm is developed for a known plaintext attack where only a small segment of plaintext is assumed to be known. Keywords. ISAAC. Keystream generator. Cryptanalysis

Study of imperfect keys to characterise the security of optical encryption

In conventional symmetric encryption, it is common for the encryption/decryption key to be reused for multiple plaintexts. This gives rise to the concept of a known-plaintext attack. In optical image encryption systems, such as double random phase encoding (DRPE), this is also the case; if one knows a plaintext-ciphertext pair, one can carry out a known-plaintext attack more efficiently than a brute-force attack, using heuristics based on phase retrieval or simulated annealing. However, we demonstrate that it is likely that an attacker will find an imperfect decryption key using such heuristics. Such an imperfect key will work for the known plaintext-ciphertext pair, but not an arbitrary unseen plaintext-ciphertext pair encrypted using the original key. In this paper, we illustrate the problem and attempt to characterise the increase in security it affords optical encryption

APLIKASI PENGIRIM EMAIL DENGAN PENERAPAN ENKRIPSI CAESAR CIPHER YANG TELAH DITINGKATKAN KEAMANANNYA MENGGUNAKAN ENKRIPSI ROW TRANSPOSITION CIPHER

Kriptografi adalah seni menulis dan memecahkan suatu kode (Concise Oxford Dictionary, 2006). Kriptografi terbagi menjadi dua, yaitu kriptografi klasik dan kriptografi modern. Enkripsi Caesar Cipher merupakan teknik enkripsi kriptografi klasik yang tidak memiliki keamanan yang baik dalam pengenkripsiannya sebab pencarian kunci enkripsi dapat dilakukan dengan mudah menggunakan teknik Known Plaintext Attack ataupun Letter Frequency. Salah satu cara untuk meningkatkan keamanan pengenkripsian Caesar Cipher adalah menggunakan penggabungan dengan metode enkripsi lain yang memiliki keamanan yang baik. Teknik enkripsi kriptografi klasik dapat dikategorikan baik apabila pencarian kunci enkripsi tidak dapat dilakukan dengan metode Known Plaintext Attack ataupun Letter Frequency, sehingga pencarian kunci hanya dapat dilakukan dengan metode Brute Force Search. Teknik enkripsi kriptografi klasik yang baik salah satunya adalah Row Transposition Cipher, sehingga dapat digunakan untuk meningkatkan keamanan pengenkripsian Caesar Cipher. Pada penelitian ini, keamanan pengenkripsian Caesar Cipher ditingkatkan menggunakan penggabungan dengan metode Row Transposition Cipher, sehingga hasil enkripsinya memiliki keamanan yang baik. Selanjutnya, teknik enkripsi tersebut diterapkan pada program aplikasi pengirim email untuk melihat bagaimana proses enkripsinya bekerja. Program aplikasi tersebut dibuat menggunakan software Delphi 7.,---Cryptography is the art of writing or solving codes (Concise Oxford Dictionary, 2006). Cryptography is divided into two, namely classical cryptography and modern cryptography. Encryption Caesar Cipher is a classic cryptographic encryption technique that does not have good security in its encryption because the encryption key can be search easily using Known Plaintext Attack or Letter Frequency method. One way to improve the security of encrypting Caesar Cipher is merging with other encryption methods that have good security. Classical cryptographic encryption techniques can be categorized as a good security encryption when the encryption key searches can not be performed by the Known Plaintext Attack or Letter Frequency method, so the encryption key can only be found by Brute Force Search method. A good classical cryptographic encryption technique, one of which is the Row Transposition Cipher, so it can be used to improve the security of Caesar Cipher encryption. In this study, the security level of Caesar Cipher improved using merging with Row Transposition Cipher method, so that the encryption results have good security. Furthermore, the encryption technique applied to the email sender application program to see how the encryption process works. The application program is created using Delphi 7 softwar