Suppose a password consists of 9 ASCII characters. You can review the ASCII characters here.. There are exactly 2" = 128 ASCII characters; we will assume every character in the password is ASCII (non-printing characters are allowed). What is the size of the keyspace that consists of passwords of this form? What is the equivalent key length in bits? Assuming that you could check one password every 10¬10 seconds, what is the worst case running time for cracking this password by brute force search (in days)? Now assume that the user used only 29 characters from the keyboard. What is the key length in bits in this case? How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here -- be as exact as possible. Supposing you used only 29 characters, how long is the shortest password that achieves 177 bits of security?

Suppose a password consists of 9 ASCII characters. You can review the ASCII characters here.. There are exactly 2" = 128 ASCII characters; we will assume every character in the password is ASCII (non-printing characters are allowed). What is the size of the keyspace that consists of passwords of this form? What is the equivalent key length in bits? Assuming that you could check one password every 10¬10 seconds, what is the worst case running time for cracking this password by brute force search (in days)? Now assume that the user used only 29 characters from the keyboard. What is the key length in bits in this case? How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here -- be as exact as possible. Supposing you used only 29 characters, how long is the shortest password that achieves 177 bits of security?

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

See similar textbooks

Similar questions

In this problem we explore the relationship between password length and cryptographic security. Suppose a password consists of 1212 ASCII characters. You can review the ASCII characters here.. There are exactly 27=12827=128 ASCII characters; we will assume every character in the password is ASCII (non-printing characters are allowed). What is the size of the keyspace that consists of passwords of this form? ___What is the equivalent key length in bits? ___ Assuming that you could check one password every 10−710−7 seconds, what is the worst case running time for cracking this password by brute force search (in days)? ___ Now assume that the user used only 2828 characters from the keyboard. What is the key length in bits in this case? ___ How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here -- be as exact as possible. ___ Supposing you used only 2828 characters, how long is the shortest password that achieves 249249 bits…
In this problem we explore the relationship between password length and cryptographic security. Suppose a password consists of 77 ASCII characters. You can review the ASCII characters here.. Exactly 27=12827=128 of these codes are for printable characters; we will assume every character in the password is printable. What is the size of the keyspace that consists of passwords of this form?What is the equivalent key length in bits? Assuming that you could check one password every 10−810−8 seconds, what is the worst case running time for cracking this password by brute force search (in days)? Now assume that the user used only 3131 characters from the keyboard. What is the key length in bits in this case? How many days, in the worst case, would it take to break this weaker password? You can't round to the nearest day here -- be as exact as possible. Supposing you used only 3131 characters, how long is the shortest password that achieves 252252 bits of security?
Consider the encryption function for a symmetric cryptosystem E(k, m) described below, where K = M = {0, 1, 2, 3}, C = {0, 1, 2, 3}: E(k, m) = (2 ∗ k + m) mod 4 (a) Give the corresponding decryption function(b) Is this cryptosystem information-theoretically secure(or perfectly secure)? Why or why not?
Consider a large institution that has 16891 employees. How many keys are necessary to allow any pair of employees to securely communicate using a symmetric cipher? Suppose that we instead use an asymmetric cryptographic scheme. How many keys are required in this case?
Question 3: Caesar Cipher we write the message and then shift the alphabet by some specified number of letters. For example, he might choose to shift the alphabet by 4 letters. Then, A is replaced by E, B is replaced by F, and so on. When we reach V, it becomes Z. After that, we go back to the beginning so that W becomes an A, X becomes a B, and so on. One approach to breaking some encryption is brute force. If we know it was a Caesar cipher, then there are only 25 possible shifts, so we can just test them all until we find one that seems right. You are required to provide a code to decrypt the following message using Brut Force technique. "GUVF VF ZL FRPERG ZRFFNTR."
Let's say you generated RSA keys and you chose p=59, q=43, and the smallest encryption exponent that qualifies for this p and q. (You will have to follow the key generation algorithm to fill in the details.) If someone gives you 99 as the ciphertext they created using your public key, what is the plaintext you get when you use your private key to decrypt? What is e?____ What is d?____ What is the decrypted value?____
What is the security requirement on password hashing? Given a password w, its hash is calculated as . This question is about the security requirement on function h. (a) Can we use any function as h for password hashing? For example, can we use the "mod 100" function, which is a common computer science function? (Given any integer value x, "mod 100" function works by "x mod 100," which is a value between [0, 99]; for example, if x = 105, x mod 100 = 5; x = 1000000, x mod 100 = 0;) (b) If not, what is the security requirement on h?
Now consider the opposite problem: using an encryption algorithm to construct a oneway hash function. Consider using RSA with a known key. Then process a message consisting of a sequence of blocks as follows: Encrypt the first block, XOR the result with the second block and encrypt again, etc. Show that this scheme is not secure by solving the following problem. Given a two-block message B1, B2, and its hash RSAH(B1, B2) = RSA(RSA (B1) +B2) Given an arbitrary block C1, choose C2 so that RSAH(C1, C2) = RSAH(B1, B2). Thus, the hash function does not satisfy weak collision resistance.
Let F be a single round of a Feistel cipher operating on 64-bit blocks. That means an input a = (aL, aR) whereaL and aR are 32 bits long each, and F(aL, aR) = (aR, aL xor f(aR, k)). f is the Feistel cipher’s ”secret” function.Suppose that (aL, aR) and (bL, bR) are a pair of plaintexts such that aR xor bR = q for some number q.Consider what happens when we run two rounds of the Feistel Cipher on the input a, and two rounds of the Feistel Cipher on b:.(cL, cR)=F(F(aL, aR)), (dL, dR)=F(F(bL, bR)) ShowthatifcL =dL,thencR xordR =q.
The definition of a Shift Cipher can be expressed as follows:Def. Let x, y, k ∈ Z26 with the encryption operation as ek(x) ≡ x + k mod 26 and thedecryption operation as dk(y) ≡ y - k mod 26.Given the provided letter encoding, what would be the encoding of the plaintext word ATTACKafter applying a shift cipher with a k=17?
An affine cipher has the form c = (am+b) mod n. Suppose m is an integer between 0 and 25, eachinteger representing a letter.(a) Let n = 26, a = 3, and b = 123. What is the ciphertext corresponding to the phrase THIS IS A CIPHERMESSAGE.(b) A requirement for a cipher is that every plaintext letter correspond to a different ciphertext letter. If either aand b is not relatively prime to n, does the affine cipher meet this property? Either prove it does or presenta counterexample.
Let the input size of a block cipher be 16 bits and the block cipher is used in the electronic code book (ECB) mode of operation. Suppose we have the following plaintext where all blocks are encrypted using the same key: (02 34 67 88 02 34 44 AB 67 88 B0 3F)hex i) Let say the encrypted important file is stored in this scheme and each data record has a size of 16 bits. The records are not related to one another. Is ECB mode still appropriate in this scenario? Please state your reason.