Saknussemm is a Transposition in two moves — the whole message written backwards, then the reversed letter stream sliced into column-shaped clusters — the runic parchment Arne Saknussemm left inside Jules Verne's "Journey to the Centre of the Earth".
Take the Plaintext, keep the letters only and reverse the stream: DESCENDE becomes EDNECSED. This is the step that stops the professor in the novel — he reads the runes for days before Axel suggests reading the message "backwards, like the people of Thule".
Choose the shape: how many letters each cluster holds (the parchment: 7) and how many clusters each line prints (the parchment: 3). Lines themselves are unlimited — the text simply flows onto as many lines as it needs.
Write the reversed stream across the rows of a grid whose columns are the clusters: letter number k of the reversed stream lands in cluster k mod W, row k div W, where W is the total number of clusters.
Read the grid down its columns and print what you see:
clustersPerLine clusters per line, separated by spaces. The
Ciphertext of DESCENDE in the parchment's shape is
EEE DCD NS — three clusters, all on one line.
Each row adds one cluster in print order. SNEFFELS reversed is
SLEFFENS; the 3-by-2 shape needs four clusters, and cluster number 1
takes every 4th letter of the reversed stream starting from the first:
S, then F. Cluster 2 takes L and E, cluster 3 takes E and N, cluster 4
takes F and S. The printed cryptogram is SF LE EN FS — four clusters,
two per line.
Everything follows from one relation: cluster k holds the letters S[k], S[k+W], S[k+2W], … where S is the reversed message and W the cluster count. Reading the clusters side by side rebuilds the grid's rows, which read across spell S — and one more reversal spells the plaintext. No letter is ever changed, duplicated or dropped: the ciphertext is always an anagram of the message, which is both the cipher's charm and its weakness.
Input is uppercased and stripped to letters before encrypting — punctuation and spaces never enter the grid. The parchment's Latin, commas and all, becomes a 133-letter stream.
The output carries spaces and line breaks on purpose: they mark the cluster boundaries. Decrypting accepts either form — the whitespace-separated clusters, or one solid blob of letters sliced with the same shape rule.
The shape defaults to the parchment's 7 and 3. Any other shape encrypts the same way, but only 7-by-3 reproduces the novel's dictation.
Type your message into the message input — letters, punctuation and case are all welcome; the cipher keeps the letters only.
Pick the shape: the letters-per-cluster picker decides how many letters each cluster holds, the clusters-per-line picker how many clusters each line prints. The parchment's own shape is 7 and 3 — the defaults.
Read the the output field field: the clusters appear line by line, space-separated, in a monospace font so the gaps stay visible.
Press the swap button the swap button to switch to decrypt mode.
Paste the cryptogram into the message input. Whitespace between the clusters is read as a cluster boundary — keep it if you can. A solid blob of letters works too; the tool slices it with the current shape rule.
Set the shape the sender used with the letters-per-cluster picker and the clusters-per-line picker. A wrong shape scrambles the rows: the letters are all there, just in the wrong grid.
Read the Plaintext in the output field — the final reversal happens automatically.
In encrypt mode, press the “Load the parchment” button: the page fills with the Latin message Axel deciphers — "descend into the crater of Yoculis at Sneffels…"
Watch the tool produce Saknussemm's scrambled clusters, then press the swap button: the clusters carry over to the input and the output side shows the Latin again — the round-trip is exact.
Now press the “Load the parchment” button in decrypt mode: the same button loads the novel's own dictation — "mm.rnlls esruel seecJde…". The tool reads it with the 7-by-3 shape and recovers the Latin message up to the parchment's quirks: the novel's transcription carries the punctuation as grid cells and skips one corroded letter.
Saknussemm looks impenetrable — backwards Latin in runic clusters — and is in fact the easiest transposition on this site to break, because the key space is two small numbers.
The cipher never substitutes a single letter: the Ciphertext is always an anagram of the Plaintext. The only secrets are the reading direction (backwards — but Axel's suggestion is the first thing any solver tries) and the shape (letters per cluster, clusters per line). Both live in a tiny space: a dozen plausible values each, searchable by hand in minutes.
Count the letters. If every letter of the language appears with its normal frequency, no substitution is at work — profile first, transposition second. On the site, /identify reports exactly this.
Read it backwards. Reverse the whole letter stream; for Latin — or any text — the ending often shows a signature or a keyword, which anchors the direction.
Sweep the shape. Reverse the stream, then try cluster counts that divide the text into even lines: the parchment prints 21 clusters, so 7 letters per cluster and 3 per line. The right shape is the one whose clusters, read side by side, spell reversed Latin.
Watch the tell. Correctly assembled rows read like language; a near-miss shape produces noise. There is no key to recover beyond the shape — once the rows read, the message is broken.
The guided crackers on this site search key spaces worth guiding through — alphabets, discs, column permutations. Saknussemm's whole key space is a pair of small integers you can sweep by hand with the shape pickers, and its single practice challenge is a text every reader of the novel already owns. A cracker would only automate the sweep; the parchment deserves the hand-work.
Verne's professor keeps the runes secret for weeks and falls to the simplest trick in the book: reading backwards. The cipher is a lesson in humility — security that rests on the adversary not trying the second obvious thing is not security at all.