![]() ![]() The formula in cell C4 returns an error if a character is not found in cell B10. Also, replace the FIND function with the SEARCH function in the formulas below or make sure that you only use upper letters in cell C2. You can change the alphabet in cell B10 to only upper letters if you want a more read-friendly code. The formulas calculate the remainder and use that number to extract a character. Sometimes the sum is larger than the number of characters in the provided alphabet. The sum is then the position of a different character in the alphabet. They then add the numbers, see image above. The formulas finds the relative position of each character of both plain text message and the code key in the alphabet, provided in cell B10. The Vigenere cipher uses the same key repeatedly across the entire message, here is a detailed explanation: Vigenere cipher The transposition cipher can be broken using frequency analysis and anagramming. ![]() The formula below adds a | character to show if the last character is the space character. ![]() The transposition cipher deploys characters in a grid based on the number of columns entered in cell C3.Ĭoncatenate characters starting from the upper left corner moving down, then continue with the next column, and so on. Res = res & amp amp amp amp amp amp amp amp amp Mid(dec, i, 1) Res = res & amp amp amp amp amp amp amp amp amp Chr(Asc(UCase(Mid(dec, i, 1))) - Range("B8")) Res = res & amp amp amp amp amp amp amp amp amp Chr(90 - (64 - (Asc(UCase(Mid(dec, i, 1))) - Range("B8")))) ![]() Res = res & amp amp amp amp amp amp amp amp amp Chr(65 + (Asc(UCase(Mid(dec, i, 1))) - Range("B8") - 91))ĮlseIf (Asc(UCase(Mid(dec, i, 1))) - Range("B8")) & amp amp amp amp amp amp amp amp lt 65 Then If (Asc(UCase(Mid(dec, i, 1))) - Range("B8")) & amp amp amp amp amp amp amp amp gt 90 Then If Asc(UCase(Mid(dec, i, 1))) & amp amp amp amp amp amp amp amp lt 91 And Asc(UCase(Mid(dec, i, 1))) & amp amp amp amp amp amp amp amp gt 64 Then Res = res & amp amp amp amp amp amp amp amp amp Mid(enc, i, 1) Res = res & amp amp amp amp amp amp amp amp amp Chr(Asc(UCase(Mid(enc, i, 1))) + Range("B8")) Res = res & amp amp amp amp amp amp amp amp amp Chr(90 - (64 - (Asc(UCase(Mid(enc, i, 1))) + Range("B8")))) Res = res & amp amp amp amp amp amp amp amp amp Chr(65 + (Asc(UCase(Mid(enc, i, 1))) + Range("B8") - 90))ĮlseIf (Asc(UCase(Mid(enc, i, 1))) + Range("B8")) & amp amp amp amp amp amp amp amp lt 65 Then If (Asc(UCase(Mid(enc, i, 1))) + Range("B8")) & amp amp amp amp amp amp amp amp gt 90 Then If Asc(UCase(Mid(enc, i, 1))) & amp amp amp amp amp amp amp amp lt 91 And Asc(UCase(Mid(enc, i, 1))) & amp amp amp amp amp amp amp amp gt 64 Then The following macro rotates each letter in cell B2 by a number found in cell B8. The message is " Want to know what it takes to work at NSA? Check back each Monday in May as we explore careers essential to protecting our nation"Ī famous substitution cipher is the Caesar cipher, rotating each letter a number of places.Īccording to wikipedia, the cipher was reasonably secure at the time because Caesar's enemies would have been illiterate. It is a basic substitution cipher meaning t=w, p=a and so on. = TEXTJOIN(, FALSE, MID(B8, FIND( MID(C5, SEQUENCE( LEN(C5)), 1), B9), 1))Ī twitter account belonging to NSA posted this weird message one morning in the beginning of May. This simple step can make it harder for a dictionary attack to recognize words. The formula in cell C4 changes the text entered in cell C3, the last character is first and the first character is last, and so on. Often the encrypted text is used to decrypt it back to plain text to make sure that the decryption formula works fine. The TEXTJOIN function requires a VBA user defined function which you can find here: How to use the TEXTJOIN functionĮach section contains a formula that encrypts plain text messages and a formula that decrypts a cipher. Some but perhaps not all formulas can be converted so they can be used in older Excel versions. Most if not all formulas presented here use functions that are only available in Excel 365. How to shuffle characters in the alphabet. ![]()
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