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Old 2010-10-14, 11:42   #1
science_man_88
 
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Default A good encryption ?

is this a good encryption method ?

Shift each character in the message by it's position.

or should a good one be more complicated.
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Old 2010-10-14, 12:06   #2
firejuggler
 
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far too simple, i would say
a good encryption method would require a 'key' as long as the message, and could be used only once.
or another possibility is the double encryption, without key transmission
A encode the message, then send it to B
B apply his own encryption key to the message and send it back to A
A decode the message with his key , then send to B
then B just have to decode the message
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Old 2010-10-14, 12:12   #3
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Quote:
Originally Posted by firejuggler View Post
far too simple, i would say
a good encryption method would require a 'key' as long as the message, and could be used only once.
or another possibility is the double encryption, without key transmission
A encode the message, then send it to B
B apply his own encryption key to the message and send it back to A
A decode the message with his key , then send to B
then B just have to decode the message

unless you send the same basic message more than once each message could be it's own key if it has to be as long as the message, but anyway I'm making stuff I couldn't easily decrypt lol
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Old 2010-10-14, 12:25   #4
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Quote:
Originally Posted by science_man_88 View Post
is this a good encryption method ?

Shift each character in the message by it's position.

or should a good one be more complicated.
It's a lousy encryption method.

Paul
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Old 2010-10-14, 13:12   #5
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Quote:
Originally Posted by firejuggler View Post
or another possibility is the double encryption, without key transmission
A encode the message, then send it to B
B apply his own encryption key to the message and send it back to A
A decode the message with his key , then send to B
then B just have to decode the message
Technically that is not an encryption method, but is a transmission method. But you don't say how you verify who B is. Authentication is very important for that sort of scheme.

Anyhow all this stuff has been solved. Lots of good schemes exist for generating a shared secret key, but we still have the authentication problem. SSL is okay, not great though unless you absolutely trust all of those root key authorities in your browser. How come we have so many root authorities? Why TF is the Hong Kong Post Office in there? Do you trust them?
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Old 2010-10-14, 13:19   #6
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Quote:
Originally Posted by science_man_88 View Post
is this a good encryption method ?

Shift each character in the message by it's position.
As a first year high school BASIC programming assignment, yes it is good for that.

the = ujh
them = ujhq
they = ujhc

method failure

Layering a word position on top of that would help, a little.
Alternately (every other word) shifting forward and backward would help, a little.
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Old 2010-10-14, 14:07   #7
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Quote:
Originally Posted by Uncwilly View Post
As a first year high school BASIC programming assignment, yes it is good for that.

the = ujh
them = ujhq
they = ujhc

method failure

Layering a word position on top of that would help, a little.
Alternately (every other word) shifting forward and backward would help, a little.
at least you seem positive yeah that's why I thought of the shifting depending on position because then instead of the=ujh all the time it could be

the=ujh at position 1
the=vki at position 2
...... at position x

the problem i see is it's still almost as bad as using constant shift because regardless we would know to shift this this way by this much so it needs more random organisation but still able for decoding.
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Old 2010-10-14, 14:17   #8
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Quote:
Originally Posted by science_man_88 View Post
at least you seem positive yeah that's why I thought of the shifting depending on position because then instead of the=ujh all the time it could be

the=ujh at position 1
the=vki at position 2
...... at position x

the problem i see is it's still almost as bad as using constant shift because regardless we would know to shift this this way by this much so it needs more random organisation but still able for decoding.
You're still not seeing the obvious: this is not an encryption system because there is no key.

Paul
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Old 2010-10-14, 14:23   #9
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Quote:
Originally Posted by xilman View Post
You're still not seeing the obvious: this is not an encryption system because there is no key.

Paul
http://en.wikipedia.org/wiki/Key_(cryptography)
states and I quote:

"In cryptography, a key is a piece of information " heres a piece of information:

shift each the place value for each characters place.
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Old 2010-10-14, 14:46   #10
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Quote:
Originally Posted by science_man_88 View Post
http://en.wikipedia.org/wiki/Key_(cryptography)
states and I quote:

"In cryptography, a key is a piece of information " heres a piece of information:

shift each the place value for each characters place.
If you are going to start quoting definitions at me, I recommend that you first read La Cryptographie Militaire, by Auguste Kerckhoffs.

Put simply, if you don't understand Kerckhoffs' Principles, you do not have a clue about what cryptography really means.


Paul
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Old 2010-10-14, 15:40   #11
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Quote:
Originally Posted by xilman View Post
Put simply, if you don't understand Kerckhoffs' Principles, you do not have a clue about what cryptography really means.
Aside from the ban on 'security through obscurity', which of the Principles do you think are still relevant today? Telegraphy isn't important, and complex methods are now acceptable thanks to the advent of general-purpose computers.
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