Encryption

hi! pliz help me here....
1) can u help me on using the public key    encryption to  show that encryption can be used NOT for security or protection?

2) how can i determine the minimum,average and maximum time it would take to crack a six-digit password if one can be checked every millisecond?
msberthAsked:
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TooKoolKrisCommented:
The purpose of public key is to encrypt data. Just because it is susceptable to being hacked doesn't mean that it's has no use in security and in data protection. It takes a lot to decrypt when a good key phrase is being used.

The time that is involved with decryption has many variables that must be defined before one could tell you the amount of time that it would take. The deeper the level of encryption the longer it's going to take. Obvoulsy the slower the CPU in your pc the longer it will take as well.

Here are some pages that you can look at:
http://www.rsasecurity.com/rsalabs/rc6/rc6_performance.html

Good PDF File:
http://www.informatik.tu-darmstadt.de/ftp/pub/TI/reports/Takagi.diss.pdf

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chicagoanCommented:



s0rry, we cann0t helP y0U w1th hOmew0rk ass1gnMENts

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TooKoolKrisCommented:
Q: how long would it take someone to crack 128 bit encryption?

When the press talks about "cracking" or "breaking" an encryption algorithm. They always seem to mean this: the "attacker" decrypted a message by guessing the secret key that was used for the encryption. This is not breaking or cracking a particular algorithm. But it does demonstrate the importance of key size. The key size -- the number of bits used to store the key, which is an integer number -- determines the size of the key space, the number of possible keys that can be used. If you knew that to decrypt a message you needed to guess a number between 1 and 10, would you feel challenged? How about between 1 and 1000? How about 1 and 1^38 (1 followed by 38 zeros). That is (roughly) the key space using a 128-bit key. For comparison purposes, let’s use a (so far) non-existent computer that can guess 1 trillion (1 followed by 12 zeroes) keys a second. On average, it would take around 2 million million million (2 followed by 18 zeroes) years to guess the key.

Public Key Cryptography: A Continuation of the Discussion
http://www.avolio.com/columns/pkiq+a.html

How PGP works
http://www.pgpi.org/doc/pgpintro/

Passwords vs Public Key Cryptography for encryption
http://www.articsoft.com/encryption.htm

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SNilssonCommented:
"s0rry, we cann0t helP y0U w1th hOmew0rk ass1gnMENts"

Nice touch,  talking to the kids in there own language :)
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shanyuenCommented:
Encryption is process to encrypt/coding and invited for security or protection.
Public key can be spreaded except private key.
But, maybe it can used for other thing.
Ex: for research only, for riddle only, to generating random character for designer :)

what you mean about "if one can be checked every millisecond?"
Are you mean 1 character every 1 millisecond ?
CPU able to check NOT one millisecond, but 1 char=1/million millisecond.
Yes, it can be cracked easly if your six digit password is the combination of numerical variable (0-9) only.
The time to crack the password is depend :
-how fast your CPU to try (brute force).
-how long your password digit.
-what variable in your password. (0-9,a-z,A-Z,all ASCII code, or the combination of thems)
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