Way back when, this code was pretty solid. You’d have a word as a key - say, Horse. Then you’d treat each letter as a corresponding number to offset your message (if we’re counting A as 0, “H-O-R-S-E” becomes “7-14-17-18-4″). Then you offset each letter in the message by the corresponding number
H+7 = O
E+14 = T
L+17 = C
L+18 = D
O+4 = S
Space is ignored but uses the 7
W+14 = K
O+17 = F
R+18 = J
L+4 = P
D+7 = K
! is also ignored but would use the 14 if the message continued.
So “Hello World!” becomes “Otcds Kfjpk!”
If the encrypted message is short, this can be quite tough to crack, but if it’s a couple pages and you suspect it’s a Vigenere you can generally break it with a multi-step process:
1) You break up the text the same way the code does. If you happen to know the key’s length you make a set of substrings. In the “Hello World!” example this would be
“O d”, “tK!”, “cf”, “dj”, “sp”
In a multi-page document each of these substrings would be quite long.
2) You then assume the most common letter of the language corresponds to the most common letter in the encrypted message. So if your most common letter in the first substring is D, you’d assume it’s being offset by 25 (aka “offset by -1,” since it’s an alphabet and you wrap around) because the most common English letter is E. To decrypt you’d offset the whole substring by [26 - offset] (in this case being 1).
3) Once you’ve done this for every substring, you collate the letters again and it reconstitutes your message.
4) With computers, at this point you can probably eyeball-crack the problem of not knowing the key length. Get the computer to perform steps 1-3 on the suspicion that it’s length 2, then 3, then 4, all the way up to 9 or 10. Then print out the first 100 characters from each result. If your target was a Vigenere Cipher, one of the messages is intelligible and the others aren’t.
areudirty
turnnoffyourmind
dailybridgerton
jacobvanloon
blakekathryn
dededos
andulkaphoto
tangentwithtanner
germansingergirl
