Gronsfeld
History
The Gronsfeld cipher was invented by the Bavarian Field Marshal Count Jobst Maximilian von Gronsfeld (1598-1662) and is a shortened variation of the Vigenère cipher using only 10 of the 26 alphabets with the key using characters in the range A-J or 0-9. Otherwise encipherment of text is performed in the same way as the periodic ciphers.
Description
The key letter is found in the left column of the table and determines the row, and the plaintext letter is found in the top row and determines the column. The intersection of these reveals the cipher letter. So using the Vigenère variation if the key is D and the plaintext letter is I the cipher letter is L.
Example
Type: Vigenère Gronsfeld
Key word: DCHFJBA (3275910)
Key: DC H FJBA DCH FJBAD CHFJB A DC HFJBADC HFJB ADC
Plaintext: If I were two-faced, would I be wearing this one?
Ciphertext: LH P BNSE WYV-KJDEG, YVZUE I EG DJJSIQI AMRT OQG?
Encipher the following Abraham Lincoln quote "If I were two-faced, would I be wearing this one?” using the keyword DCHFJBA gives:
Vigenère Cipher
If I were two-faced, would I be wearing this one?
LH P BNSE WYV-KJDEG, YVZUE I EG DJJSIQI AMRT OQG?
Beaufort Cipher
If I were two-faced, would I be wearing this one?
VX Z JFKW KGT-AJZWA, GTLYY S CY LBJKSQW OYBJ MQY?
Variant Beaufort Cipher
If I were two-faced, would I be wearing this one?
FD B RVQE QUH-ARBEA, UHPCC I YC PZRQIKE MCZR OKC?
Porta Cipher
If I were two-faced, would I be wearing this one?
WT Y HVER FIL-URPRR, ILFPQ V PS GTREVMU DWZF BMS?
Solving
Solving method: Brute force search.
After selecting the Gronsfeld cipher, the cipher period can be selected from the Setup drop down menu. The default setting of 0 will result in all periods in the keyword range set in the Options window being tested.
Gronsfeld Vigenère Table
Gronsfeld Beaufort Table
Gronsfeld Variant Beaufort Table
Gronsfeld Porta Table