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Key Space and Brute Force Attacks
Hewlett-Packard Company Virtual Private Networking Concepts Guide
2-13
Key Space and Brute Force Attacks
Key Space and Brute Force AttacksKey Space and Brute Force Attacks
Key Space and Brute Force Attacks
Before reading this section, review Symmetric Cryptographic
Systems (page 2-3) and Asymmetric Cryptographic Systems
(page 2-9).
Key Space
Key SpaceKey Space
Key Space In the simple cryptographic systems, up to 26 different possible
keys can be selected. The keys available range from 1 to 26 since
there are 26 letters in the alphabet. If 27 is used as your key, it
would produce the same cipher text as if 1 was selected for your
key. Therefore, your key space contains exactly 26 keys.
The longer the key length, the more possible combinations a
potential code-breaker would have to test. The following table
shows the number of possibilities for common key length
(Source: FreeMarket.Net: Policy Spotlight, October-November
1997).
Brute Force
Brute Force Brute Force
Brute Force
Attacks
AttacksAttacks
Attacks
A brute force attack captures some cipher text and then tries all
26 different possible keys. Given enough cipher text, a brute
force attack could be quite effective. Obviously, if you can
increase the number of different keys available, brute force
attacks become correspondingly more difficult or time
consuming. The trick is to find an algorithm that allows for an
extremely large number of keys. The higher the key space, the
more difficult the encryption is to break.
Related
Related Related
Related
Information
InformationInformation
Information
Symmetric Cryptographic Systems (page 2-3)
Asymmetric Cryptographic Systems (page 2-9)
Key Length
Key LengthKey Length
Key Length Possible Keys
Possible KeysPossible Keys
Possible Keys
40 bits 1,099,511,627,776
56 bits 72,057,594,037,927,900
90 bits 1,237,940,039,285,380,000,000,000,000
128 bits 340,282,366,920,938,000,000,000,000,000,000,000,000