Quiz TWO and Final Exam Study Guide - 810:023 - 04/03/2010
ABCDEFGHIJKLMNOPQRSTUVWXYZ
DEFGHIJKLMNOPQRSTUVWXYZABC
A becomes D,
B becomes E,
C becomes F,
... , Y becomes B, and
Z becomes C
when Caesar key = 3 and you are ENCRYPTING the original message.
ABCDEFGHIJKLMNOPQRSTUVWXYZ
DEFGHIJKLMNOPQRSTUVWXYZABC
A becomes D, B becomes E, C becomes F, ... , Y becomes B, and Z becomes C when Caesar key = 3.
To decrypt, you go backwards 3 letters.
So the ciphertext message has D becoming A,
E becoming B, ...
...
A becoming X,
B becoming Y, and
C becoming Z
when you DECRYPT from cipher text to plain text.
Plain text is the term for the original, readable, unencrypted message.
wokqcovigsugkocmgycnu is the cipher text. You have to do this by hand, with paper and pencil!
A becomes a C (2 letter shift) if A was an ODD letter, 1st, 3rd, 5th, etc.
A becomes a B (1 letter shift) if A was an EVEN letter, 2nd, 4th, 6th, 8th, etc.
Thus the code used to ENCRYPT, to create the CIPHER TEXT is CB.
21.
ABCDEFGHIJKLMNOPQRSTUVWXYZ ABCDEFGHIJKLMNOPQRSTUVWXYZ
CDEFGHIJKLMNOPQRSTUVWXYZAB BCDEFGHIJKLMNOPQRSTUVWXYZA
2 letter shift, also called 1 letter shift, also called
code C, because A becomes C code B, since A becomes B, when encrypting the message to ciphertext.
when encrypting to cipertext...
C becomes A when decrypting B becomes A when decrypting ciphertext back to plaintext, back to the message.
back to plaintext!
2 1
C B
C B = CB
2 1 = 21
bash-2.03$ mkdir MAY4th
bash-2.03$ cd MAY4th
bash-2.03$ pwd
/export/home/jacobson/MAY4th
bash-2.03$ ls -a
. .. What are .. and . for?
bash-2.03$ ls ../*b*.txt
../bc.txt ../lastMondayFeb22nd.txt
../bc55.txt ../whoWasHereOnFeb25in025.txt
../bcOutput.txt
../whoWasHereOnFridayJoanOsbourne.txt
WHAT DO ALL THESE FILES ABOVE HAVE IN COMMON????
They all contain the letter b, lowercase b!
ls ../*b*.txt
-
*b*.txt means match or find all files
that contain a little b anywhere,
and end in the extension .txt
* characters are called wildcards!
---------
bash-2.03$ cp ../bc55.txt . NOTE THE USE of .. and .
-- - -- -
.. . .. .
-- - -- -
parent current parent current
directory directory folder folder
bash-2.03$ ls -a
. .. bc55.txt
bash-2.03$ ls -a ls for list files and folder
- -- --------
. .. bc55.txt -a for all -a = -all
- -- -------- ---
. ..
bash-2.03$ cp ../bc55.txt .
COPY = cp
copy the parent directory file named bc55.txt
to the current directory
bash-2.03$ ls -l
-rw-r--r-- 1 jacobson faculty 122 May 4 15:04 bc55.txt
-rw-r--r-- 1 jacobson faculty 122 May 4 15:04 bc55.txt
110100100
6 4 4
bash-2.03$ mkdir may5th
bash-2.03$ ls -l
-rw-r--r-- 1 jacobson faculty 122 May 4 15:04 bc55.txt
drwxr-xr-x 2 jacobson faculty 4096 May 4 2010 may5th
-rw-r--r-- 1 jacobson faculty 122 May 4 15:04 bc55.txt
110100100
6 4 4
drwxr-xr-x 2 jacobson faculty 4096 May 4 2010 may5th
111101101
7 5 5
The d that starts the -l LOOOOOOOOOOOONG listing for may5th folder
indicates that may5th is a FOLDER, is a
directory.
-
mkdir may5th
created that folder named may5th.
mkdir is short for make directory
- - ---
m k dir = mkdir
- - --- -----
bash-2.03$ pwd
/export/home/jacobson/MAY4th
bash-2.03$ cd may5th
bash-2.03$ pwd
/export/home/jacobson/MAY4th/may5th
bash-2.03$ ls ../../*.c
../../tortois.c ../../tortoisSlower.c
bash-2.03$ cp ../../*.c .
bash-2.03$ ls -l
-rwx--xr-x 1 jacobson faculty 2405 May 4 2010 tortois.c
-rw-r--r-- 1 jacobson faculty 2415 May 4 2010 tortoisSlower.c
Q1: What number was used to change the permissions on the tortois.c
file, given the output of LS minusL (ls -l) that is shown below?
bash-2.03$ chmod ??? tortois.c
bash-2.03$ ls -l tortois.c
--wx-w-r-x 1 jacobson faculty 2405 May 4 2010 tortois.c
Q2: Given that chmod 762 was just done on the tortoisSlower.c file,
show what the 9 characters would be that the LS minusL command
would exhibit? Note: What would you see instead of #########?
bash-2.03$ chmod 762 tortoisSlower.c
bash-2.03$ ls -l tortoisSlower.c
-######### 1 jacobson faculty 2415 May 4 2010 tortoisSlower.c
Each # has to either be a r for read or w for write or x for execute
- - -
or else is a hyphen indicating that
given r or w or x permission is NOT allowed.
- - - ---
HERE ARE THE CORRECT ANSWERS Explained and SHOWN to the above question:
The answers are for checking your work to make sure it is correct!
-------
bash-2.03$ ls -l
--wx-w-r-x 1 jacobson faculty 2405 May 4 2010 tortois.c
011010101
wx w r x
011 = 3 CHMOD 325 i.e. chmod 325 tortois.c
010 = 2 ---
101 = 5 --- 011 010 101
3 2 5
-wx -w- r-x
0 0 0 0
11 1 1 1
011 010 101
3 2 5
-rwxrw--w- 1 jacobson faculty 2415 May 4 2010 tortoisSlower.c
111110010
7 6 2
111 = 7
110 = 6
010 = 2
bash-2.03$ chmod 325 tortois.c
bash-2.03$ chmod 762 tortoisSlower.c
bash-2.03$ ls -l
--wx-w-r-x 1 jacobson faculty 2405 May 4 2010 tortois.c
-rwxrw--w- 1 jacobson faculty 2415 May 4 2010 tortoisSlower.c
4. What do the permissions need to be for the random.cgi file?
8. See cd cgi and cd .. and pwd
and answer in context the practice questions shown on that page:
Question to find the answer for:
What would be output right now if I do the following command?
ls ..
What would be output right now if I do the following command?
ls -l LS minus L or LS hyphenL for ls -l