Tham khảo tài liệu 'hacker professional ebook part 149', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | by benina Learning About Cryptography A Basic Introduction to Crypto A Ciphers By Ritter Page Terry Ritter Current Version 1999 Jan 09 For some reason good cryptography is just much harder than it looks. This field seems to have a continuous flow of experts from other fields who offer cryptographic variations of ideas which are common in their other field. Now there is nothing wrong with new ideas. But there are in fact many extremely intelligent and extremely well-educated people with wide-ranging scientific interests who are active in this field. It is very common to find that so-called new ideas have been previously addressed under another name or as a general concept. Try to get some background before you get in too deep. You may wish to help support this work by patronizing Ritter s Crypto Bookshop. Contents The Fundamental Idea of Cryptography A Concrete Example o A Simple Cipher o Enciphering o Deciphering o The Single Transformation o Many Transformations o Weak and Strong Transformations o Keyspace o Digital Electronic Ciphering o Huge Keys Naive Ciphers Naive Challenges What Cryptography Can Do What Cryptography Can Not Do Cryptography with Keys Problems with Keys Cryptography without Keys Keyspace Strength System Design And Strength Cryptanalysis versus Subversion Secret Ciphers Hardware vs. Software Ciphers Block Ciphers Stream Ciphers Public Key Ciphers The Most Important Book Classical Cryptanalysis Other Books Coding Theory For Designers The Fundamental Idea of Cryptography It is possible to transform or encipher a message or plaintext into an intermediate form or ciphertext in which the information is present but hidden. Then we can release the transformed message the ciphertext without exposing the information it represents. By using different transformations we can create many different ciphertexts for the exact same message. So if we select a particular transformation at random we can hope that anyone wishing to expose the message break the .
