Lab – Compare Data with a Hash
Lab – Compare Data with a
Hash
Objectives
Use a
hashing program to verify the integrity of data.
Background / Scenario
It is
important to understand when data has been corrupted or it has been tampered
with. A hashing program can be used to verify if data has changed, or if it has
remained the same. A hashing program performs a hash function on data or a
file, which returns a (usually much shorter) value. There are many different
hash functions, some very simple and some very complex. When the same hash is
performed on the same data, the value that is returned is always the same. If
any change is performed on the data, the hash value returned will be different.
Required Resources
•
PC with Internet access
Step 1: Create a
Text file
a.
Search your computer for
the Notepad program and open it.
b.
Type some text in the
program.
c.
Choose File > Save.
d.
Navigate to Desktop.
e.
Type Hash in the File name:
field, and click Save.
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Step 2: Install HashCalc
b.
Click Download in the HashCalc
2.02 row.
c.
Open the hashcalc.zip file and run the setup.exe file inside.
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d.
Follow the installation
wizard to install HashCalc. Ask your instructor to help if you have any
questions about the installation.
e. Click Finish on the last screen, and close
the README file if it opened. You
may read the file if you wish.
f.
HashCalc is now installed
and running.
Step 3: Calculate
a hash of the Hash.txt file
a.
Set the following items in
HashCalc:
1)
Data Format: File.
2) Data: Click the
… button next to the Data field,
navigate to the Desktop and choose
the Hash.txt file.
3)
Uncheck HMAC.
4)
Uncheck all hash types
except MD5.
b.
Click the Calculate button. What is the value
next to MD5?
Step 4: Make a change to the Hash.txt file
a.
Navigate to the Desktop and open the Hash.txt file.
b.
Make a minor change to the
text, such as deleting a letter, or adding a space or period.
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c.
Click File > Save, and close Notepad.
Step 5: Calculate a new hash of the Hash.txt file
a.
Click the Calculate button in HashCalc again.
What is the value next to MD5?
Is the
value different from the value recorded in Step 3?
b.
Place a check mark next to
all of the hash types.
c.
Click Calculate.
d.
Notice that many of the
hash types create a hash of a different length. Why?
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