Ciphers
Bifid
Polybius coordinates written in two rows, read across by period, turned back into letters. Fractionation and transposition in one.
Cipher / Fractionation
Bifid Cipher
Polybius coordinates, split and re-read.
- Keyspace
- 25! × period variants
- Decode
- same options back
- Works on
- A-Z, J as I, the rest dropped
- Family
- 10 in fractionation
required 0 / 2
Options
Access
- Create
create("bifid") - CLI
ciphers encode bifid 'FLEE AT ONCE' --key BICONDITIONAL --period 5 - Tryplayground with the sample above
- Kinpolybius, nihilist, morse, fractionated-morse +5
Delastelle's Bifid takes each letter's row and column from a 5×5 square, writes all the rows above all the columns in blocks of period letters, then reads each block row by row in pairs and looks the pairs up again. One letter's coordinates end up spread over two output letters, and that spread is what makes it stronger than plain Polybius. The square is the one Playfair builds - key first, J folded into I. Default period is 5. Non-letters are dropped, output is uppercase.
const bifid = create("bifid");
bifid.encode("FLEE AT ONCE", { key: "BICONDITIONAL", period: 5 }).text; // "GTDUXDBTUM"
bifid.encode("FLEE AT ONCE", { period: 5 }).text; // "HAAEVSLDSP"
bifid.decode("GTDUXDBTUM", { key: "BICONDITIONAL", period: 5 }).text; // "FLEEATONCE"
period must be a positive integer. Longer than the text means the whole text is one block.