Chaocipher: Difference between revisions
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Cipher text: OAHQHCNYNXTSZJRRHJBYHQKSOUJY
Decipher text: WELLDONEISBETTERTHANWELLSAID</pre>
=={{header|BASIC}}==
{{Works with|PowerBasic and FreeBasic}}
<SyntaxHighlight lang="BASIC">
' Caocipher Example
' Rosetta Code
' This code was made in Power Basic 3.5 for DOS
CLS
' Left Alphabet
Function AlphaLeft(ct as String, pt as String, CharPos as Integer) as String
Dim tStr as String: tStr=ct
' 1. Shift the entire left alphabet cyclically so the ciphertext letter
' just enciphered is positioned at the zenith (i.e., position 1).
tStr=Right$(ct, Len(ct)-CharPos+1)+Left$(ct, CharPos-1)
' 2. Extract the letter found at position zenith+1 (i.e., the letter to
' the right of the zenith), taking it out of the alphabet, temporarily
' leaving an unfilled "hole"
Dim Hole as String: Hole=Mid$(tStr, 2, 1): Mid$(tStr, 2, 1)=" "
' 3. Shift all letters in positions zenith+2 up to, and including, the
' nadir (zenith+13), moving them one position to the left
tStr=Left$(tStr, 1)+Mid$(tStr, 3, 12)+" "+Right$(tStr, 12)
' 4. Insert the just-extracted letter into the nadir position
' (i.e., zenith+13)
Mid$(tStr, 14, 1)=Hole
AlphaLeft=tStr
End Function
' Right Alphabet
Function AlphaRight(ct as String, pt as String, CharPos as Integer) as String
Dim tStr as String: tStr=pt
' 1. Shift the entire right alphabet cyclically so the plaintext letter
' just enciphered is positioned at the zenith.
tStr=Right$(tStr, Len(tStr)-CharPos+1)+Left$(tStr, CharPos-1)
' 2. Now shift the entire alphabet one more position to the left (i.e.,
' the leftmost letter moves cyclically to the far right), moving a new
' letter into the zenith position.
tStr=Right$(tStr, 25)+Left$(tStr, 1)
' 3. Extract the letter at position zenith+2, taking it out of the
' alphabet, temporarily leaving an unfilled "hole".
Dim Hole as String: Hole=Mid$(tStr, 3, 1): Mid$(tStr, 3, 1)=" ":
' 4. Shift all letters beginning with zenith+3 up to, and including, the
' nadir (zenith+13), moving them one position to the left.
tStr=Left$(tStr, 2)+Mid$(tStr, 4, 11)+" "+Right$(tStr, 12)
' 5. Insert the just-extracted letter into the nadir position (zenith+13)
Mid$(tStr, 14, 1)=Hole
AlphaRight=tStr
End Function
Function Encode(Text as String, ct as String, pt as String) as String
Dim t as Integer
Dim tStr as String: tStr=""
For t=1 to Len(Text)
Dim Char as String: Char=Mid$(Text, t, 1)
Dim CharPos as Integer: CharPos=Instr(pt, Char)
ct=AlphaLeft(ct, pt, CharPos)
pt=AlphaRight(ct, pt, CharPos)
tStr=tStr+Left$(ct, 1)
Next
Encode=tStr
End Function
' Deciphering a Chaocipher-encrypted message is identical to the steps used
' for enciphering. The sole difference is that the decipherer locates the
' known ciphertext letter in the left (ct) alphabet, with the plaintext
' letter being the corresponding letter in the right (pt) alphabet
'
' Alphabet permuting is identical in enciphering and deciphering
Function Decode(Text as String, ct as String, pt as String) as String
Dim t as Integer
Dim tStr as String: tStr=""
For t=1 to Len(Text)
Dim Char as String: Char=Mid$(Text, t, 1)
Dim CharPos as Integer: CharPos=Instr(ct, Char)
ct=AlphaLeft(ct, pt, CharPos)
pt=AlphaRight(ct, pt, CharPos)
tStr=tStr+Right$(pt, 1)
Next
Decode=tStr
End Function
' Start of Main Code
' LEFT (Cipher Text): HXUCZVAMDSLKPEFJRIGTWOBNYQ
Dim tLeft as String: tLeft="HXUCZVAMDSLKPEFJRIGTWOBNYQ"
' RIGHT (Plain Text): PTLNBQDEOYSFAVZKGJRIHWXUMC
Dim tRight as String: tRight="PTLNBQDEOYSFAVZKGJRIHWXUMC"
' Cipher Message (Used to verify a good encoding)
Dim cText as String: cText="OAHQHCNYNXTSZJRRHJBYHQKSOUJY"
' Plain Text Message
Dim pText as String: pText="WELLDONEISBETTERTHANWELLSAID"
Print " Plain Text: "; pText: Print
Dim ctLeft as String: ctLeft=tLeft
Dim ptRight as String: ptRight=tRight
' Final Cipher Text
Dim eText as String: eText=Encode(pText, ctLeft, ptRight)
Print " Cipher Text: "; eText: Print
If eText=cText then Print "Successful" else Print "Failed"
ctLeft=tLeft: ptRight=tRight
Dim dText as String: dText=Decode(eText, ctLeft, ptRight)
Print: Print " Plain Text: "; dText: Print
If dText=pText then Print "Successful" else Print "Failed"
</SyntaxHighlight>
<pre>
Plain Text: WELLDONEISBETTERTHANWELLSAID
Cipher text: OAHQHCNYNXTSZJRRHJBYHQKSOUJY
Successful
Plain Text: WELLDONEISBETTERTHANWELLSAID
Successful
</pre>
=={{header|C}}==
{{trans|Kotlin}}
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