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My New Cipher; Quite Interesting!!
Topic Started: Apr 15 2008, 07:17 AM (895 Views)
Paarth Dave May 10 2008, 05:20 AM Post #46
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 Is it necessary that in a one-time pad, the length of the keyword has to be equal to the length of the plaintext? What if the plaintext is more than 26 characters? Then it is obvious that the keyword will not be random.

Cryptography Vanquished....
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jdege May 10 2008, 05:53 AM Post #47
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Paarth Dave
May 9 2008, 11:20 PM
Is it necessary that in a one-time pad, the length of the keyword has to be equal to the length of the plaintext? What if the plaintext is more than 26 characters? Then it is obvious that the keyword will not be random.

It is absolutely necessary that the key be longer than the message. And a key that doesn't include repeated characters is anything but random.

Random means, first, that the probability that any given character is any particular letter is 1/26. So if you have two letters, the probability that they will be the same is 1/26.
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
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Paarth Dave May 10 2008, 05:57 AM Post #48
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 And how do you decipher a two-time pad?

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Revelation May 10 2008, 09:09 AM Post #49
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 You could look at this topic, it's a two-time pad challenge. Donald also wrote a program to search for cribs.

It's not easy to crack a two time pad without cribs.
RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN
RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN
RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN
RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN
RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN
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Paarth Dave May 10 2008, 09:20 AM Post #50
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Quote:
 
It's not easy to crack a two time pad without cribs.


What are cribs? How do they help to crack a two-time pad?

Cryptography Vanquished....
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Revelation May 10 2008, 10:24 AM Post #51
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 A crib is a piece of text, most likely a word, that you know for sure is in the text. Read the links I gave you, it will show how you can use the crib.
RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN
RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN
RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN
RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN
RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN
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Paarth Dave May 10 2008, 12:32 PM Post #52
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 Thank You.

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