Columnar Transposition Decryptor

Ragged unpadded stable alphabetical key column transposition, row-major input, no fabricated cells. Classical educational encoding only; not secure encryption, no hidden normalization or inferred key.

Description

Reversing columnar transposition requires recovering each column's actual length.

Reversing columnar transposition requires recovering each column's actual length.^[1]

The shorter final-row columns must be assigned before reconstructing row-major text. Use Columnar Transposition Decryptor to evaluate the supplied inputs under the specific model below.

When to use Columnar Transposition Decryptor

Use Columnar Transposition Decryptor to evaluate the supplied inputs under the specific model below. Choose the intended encoding, alphabet or check and keep the exact character, key and measurement conventions described below.

How to use Columnar Transposition Decryptor and understand its results

Choose the intended encoding, alphabet or check and keep the exact character, key and measurement conventions described below.
Enter Text, Key using the field table and validation rules below, then run the tool.
Read Transformed and interpret units, signs, ordering and placeholders as explained below.
If the tool reports an input error, correct that field and rerun. A successful false result, empty match list or unknown-evidence placeholder has the specific meaning described here; check the limitations before applying the result.

Input field	Meaning	Value type	Requirement
text	Text	string	Required; constraints below
key	Key	string	Required; constraints below

Enter uppercase A–Z ciphertext and a nonempty uppercase key of at most 128 letters. Use stable alphabetic key ordering with left-to-right duplicate ties. Reconstruct each original column's length as floor(textLength/keyLength), plus one for columns before the remainder, then read the restored rows. No padding is removed and empty ciphertext is accepted.

originalColumnLength[c] = floor(n/keyLength)+(c<n mod keyLength ? 1 : 0); restore row-major text

Field order, units and branch conditions follow the implementation explanation above.

Output field	Meaning	Value type
transformed	Transformed	string

json

{
  "input": {
    "text": "BDACE",
    "key": "BA"
  },
  "output": {
    "transformed": "ABCDE"
  }
}

Limitations and assumptions

The shorter final-row columns must be assigned before reconstructing row-major text. Apply the exact scope and assumptions described above.

All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are stated above; extremely large inputs or outputs can also be rejected. These errors differ from successful results such as false, no matches or unknown evidence.

This educational transformation or format check does not establish modern cryptographic confidentiality, authentication or key security.

Alternative or Complementary methods

Use Scytale Transposition Tool for a related task: Scytale-style transposition rearranges text through a chosen column count.

Use Transposition Column-Count Candidate List for a related task: A column-transposition hypothesis assigns text to a rectangular or ragged grid.

References

Columnar Transposition Decryptor — tool.io

Similar or alternative tools

Scytale Transposition Tool
Scytale-style transposition rearranges text through a chosen column count.
Transposition Column-Count Candidate List
A column-transposition hypothesis assigns text to a rectangular or ragged grid.