![]() ![]() The connection strings are mostly stored in web.config. For example: a connection string can tell your web application to connect to X database at ServerA by using Z username and Y password. A for loop is added using a variable (t) that iterates starting at an epoch time that is well before the time thought to have been used to seed the random number generator, and ending at an epoch time well after.Web applications use connection strings to connect to databases with certain credentials and other configuration. To find this, first modify the C program that you included in your question, as shown below. It also illustrates how easy it is for a hacker to brute-force an encryption key, given a small amount of known plaintext and some insight into how the key may have been generated.Īlice's encryption key is: 95fa2030e73ed3f8da761b4eb805dfd7. But, it's a fun exercise - and more importantly, it highlights the reason that strong random number generators are so critical in cryptography. I agree with multithr3at3d that this question smells like a homework problem. However, since Alice used time() to seed her random number generator, you should be able to find out her key easily. If the key was generated correctly, this task will not be possible. You should write a program to try all the possible keys. Your job is to help Bob find out Alice’s encryption key, so you can decrypt the entire document. Moreover, Bob also knows the Initial Vector (IV) from the encrypted file (IV is never encrypted). ![]() Since AES is a 128-bit cipher, the 16-byte plaintext consists of one block of plaintext, so Bob knows a block of plaintext and its matching ciphertext. Based on the meta data of the encrypted file,he knows that the file is encrypted using aes-128-cbc. Therefore, Bob easily got the first 16 bytes of the plaintext. The next 8 bytes of the data are quite easy to predict as well. Around the time when the file was created, PDF-1.5 was the most common version, i.e., the header starts with %PDF-1.5, which is 8 bytes of data. The beginning part of the header is always the version number. Since the file is a PDF file, which has a header. He guessed that the key may be generated within a two-hour window 1 before the file was created. He also noticed the timestamp of the encrypted file, which is “ 23:08:49”. Since Alice is CEO of a big company, this file is very valuable.īob cannot get the encryption key, but by looking around Alice’s computer, he saw the key-generation program, and suspected that Alice’s encryption key may be generated by the program. A few month later, Bob broke into her computer and gets a copy of the encrypted tax return. To protect the file, she encrypted the PDF file using a key generated from the program described above.She wrote down the key in a notebook, which is securely stored in a safe. ![]() On April 17, 2018, Alice finished her tax return, and she saved the return (a PDF file) on her disk.
0 Comments
Leave a Reply. |