Code archives/Algorithms/Vernam-Cipher | Encryption & Decryption
This code has been declared by its author to be Public Domain code.
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| Those two functions let you encrypt&decrypt strings easly with a provided password. It is pretty secure with a strong & long password. Only ways to break the encryption is: -Bruteforce (yeah lol) -Frequency analysis of the letters Note for those who know how Vernam works: My functions repeat the keyword/password if its shorter than the string you are manipulating | |||||
;ozzi789 - 30.01.2012
original_string$="Vernam ist toll"
Print "Original String: "+original_string$
encrypted_string$= vernam_enc(original_string$,"secret1")
Print "Encrypted String: "+encrypted_string$
decrypted_string$=vernam_dec(encrypted_string$,"secret1")
If original_string$=decrypted_string$
Print "Decrypted String: "+decrypted_string$
Else
Print "This should not happen :'("
EndIf
Function vernam_enc$(strng$,key$)
len_strng=Len(strng$)
len_key=Len(key$)
key_index=1
For x=1 To len_strng
current_strng$=Mid(strng$,x,1)
current_key$=Mid(key$,key_index,1)
new_strng$=new_strng$+Chr(Asc(current_strng$)+Asc(current_key$))
key_index=(x Mod len_key)+1
Next
Return new_strng$
End Function
Function vernam_dec$(strng$,key$)
len_strng=Len(strng$)
len_key=Len(key$)
key_index=1
For x=1 To len_strng
current_strng$=Mid(strng$,x,1)
current_key$=Mid(key$,key_index,1)
new_strng$=new_strng$+Chr(Asc(current_strng$)-Asc(current_key$))
key_index=(x Mod len_key)+1
Next
Return new_strng$
End Function |
Comments
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| SWEET! I can use this to encrypt my map data even further! Thanks, Ozzi! =D |
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| Glad i could help ! :) |
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| I'll test this for data encryption/decryption in my game project. This is extremely interesting considering what I just read about the Vernam Cipher. // EDIT: It's working :) |
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| I love encryption stuff, thanks for posting 'Vernam-Cipher'. |
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| Can someone show an example or site that has this exact function only in PHP, javascript, jquery, or JSON? thanks! |
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| The Vernam Cipher {Crypto Museum} -- http://tinyurl.com/kzo37zx Inside the world of Ciphers {in Java} -- http://tinyurl.com/m3wz2dw Javascript - simple vernam cipher -- http://tinyurl.com/nm47u22 GitHub Gist Vernam Cipher in JS -- http://tinyurl.com/nast2jb Vernam Cipher in C# {CodeProject } -- http://tinyurl.com/l3cbyrf Vernam Cipher in Java {dream in code} -- http://tinyurl.com/n2zzz56  |
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| This is essentially a one-time pad and thus is secure. But he says this: My functions repeat the keyword/password if its shorter than the string you are manipulating If it does that, it is instantly zero security (due to differential cryptanalysis) so shouldn't be used for anything serious with keys shorter than the message. The problem with sufficiently long keys becomes key exchange. |
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| Then tell us, oh wise one. How would you fix this script then? |
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| Use a key as long as the message.... |
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When you use:VERNAM_DEC$(E$,Left$(K$,Rand(1,Len(K$)))) You get a partial answer to the original text. I did it this way to see if this could be a weak spot in the cypher. Is it? |
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| Not if you do it right. ~GF |
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