An implementation of Finnish WW2 era Vigenère cipher "Salakirjoitusviivain", colloquially also known as "matolaatikko."

• Uses a hardcoded letter sheet. Support for reading the key from a file exists.
• Uses hardcoded 4th group PIAEL -3+1-3-4-2 scrambling when encrypting.
• Uses hardcoded 4th group -3+1-3-4-2 when decrypting. The key order is brute-forced.
• Does not support the second row of the ruler. Supported replacements:
  • Swedish numerals (1->ett, 2->tva, etc.)
  • Space encoded as X
  • Period encoded as W
  • Repeating character encoded as C.

• key generation