A simulator of the HC-9, a mechanical cipher machine built by Transvertex in the early '50s. Based on the description from Cryptomuseum Transvertex HC-9
HC-9 is a masterpiece of mechanical engineering and was used for messages that had to remain secret for a few hours. The key space of the HC-9 compares quite favourably with German Enigma (see Cipher Machines Transvertex HC-9 )
A simple encryption/decryption example is provided in the project:
Suppose that we need to transmit the following message:
MEET ME TOMORROW AT MIDNIGHT AT THE USUAL PLACE
Using a randomly picked rotor settings: BLVGM ,we get the message to transmit
FQLMJ CJCCE PVBFC NYGCT BAANK IKXOO TPYCE PZOP
on the other side, when the message is received, with the same rotor settings (BLVGM) we get back the original message
MEETM ETOMO RROWA TMIDN IGHTA TTHEU SUALP LACE
The key space of HC-9 can be calculated for various combinations of rotors and whether all the positions of the rotors can be used as initial state. (see Calculation of the Key Space of the HC-9 in Cipher Machines Transvertex HC-9). As stated in this page, [...] The theoretical key space for the Enigma is 3.28 X 10 ^ 114 but the practical key space was greatly reduced to 1.07 X 10^23 [...]
HC-9 Key Space with 5 rotors , using Letters only for initial state rotors combinations: 11,881,376 rotors pins combinations: 2,923,003,274,661,805,836,407,369,665,432,566,039,311,865,085,952 alphabets combinations: 126,493,657,289,880 = 4,393,036,292,980,624,879,041,381,919,139,963,735,122,550,448,068,968,993,938,046,986,485,760 ~ 4.393 x 10^69 Key space: ~ 4.393 x 10^69 . The key space is larger than the practical key space of Enigma.
HC-9 Key Space with 5 rotors , using all positions for initial state rotors combinations: 35,303,730 rotors pins combinations: 2,923,003,274,661,805,836,407,369,665,432,566,039,311,865,085,952 alphabets combinations: 126,493,657,289,880 = 13,053,249,654,550,859,762,451,723,276,849,340,675,234,757,146,815,815,166,556,503,854,284,800 ~ 1.305 x 10^70 Key space: ~ 1.305 x 10^70
This is not practical for the design and size of HC-9 as one of the biggest issues would be that the alphabets' drum would be large and hard to be accomodated by such a small machine. But for the sake of comparison, IF HC-9 had rotors with these pin sizes: [29, 31, 33, 34, 35, 37, 41, 47, 53, 59]
rotors combinations: 8,031,810,176 rotors pins combinations: 883,423,532,389,192,164,791,648,750,371,459,257,913,741,948,437,809,479,060,803,100,646,309,888 alphabets combinations: 505,974,629,157,984 = 3,590,137,980,724,869,295,443,467,174,738,845,665,334,668,728,251,068,248,370,258,330,046,241,824,933,085,486,071,984,152,379,392 ~ 3.590 x 10^96 Key space: ~ 3.590 x 10^96
rotors combinations: 53,555,758,410 rotors pins combinations: 883,423,532,389,192,164,791,648,750,371,459,257,913,741,948,437,809,479,060,803,100,646,309,888 alphabets combinations: 505,974,629,157,984 = 23,938,882,784,954,196,689,620,225,634,062,454,378,271,804,192,549,203,111,811,619,507,234,550,871,008,264,315,327,937,742,110,720 ~ 2.393 x 10^97 Key space: ~ 2.393 x 10^97
rotors combinations: 2,517,120,645,270 rotors pins combinations: 124,330,809,102,446,660,538,845,562,036,705,210,025,114,037,699,336,929,360,115,994,223,289,874,253,133,343,883,264 alphabets combinations: 1,011,949,258,311,872 = 316,695,234,294,301,132,532,726,160,402,984,597,526,383,372,676,155,509,907,711,375,026,531,057,776,126,730,051,013,851,441,059,443,793,297,837,916,160 ~ 3.166 x 10^113 Key space: ~ 3.166 x 10^113
rotors combinations: 133,407,394,199,310 rotors pins combinations: 1,119,872,371,088,902,105,278,721,140,284,222,139,060,822,748,617,324,767,449,994,550,481,895,935,590,080,472,690,438,746,635,803,557,888 alphabets combinations: 2,023,898,516,607,360 = 302,368,930,299,011,461,928,063,197,625,643,153,015,243,437,999,749,738,874,352,461,094,538,054,925,911,739,488,542,240,354,647,802,094,247,975,051,465,718,497,511,525,580,800 ~ 3.023 x 10^131 Key space: ~ 3.023 x 10^131
rotors combinations: 7,871,036,257,759,290 rotors pins combinations: 645,562,469,521,727,147,413,979,793,000,752,968,582,426,448,207,305,878,207,664,839,135,161,905,504,210,298,657,411,338,320,034,457,858,975,792,993,186,873,344 alphabets combinations: 4,047,797,033,149,184 = 20,567,850,881,602,244,475,951,023,959,801,460,394,840,945,394,439,340,295,798,069,676,872,155,800,265,056,569,888,963,752,461,034,955,842,616,942,617,856,217,167,014,924,446,876,414,531,507,941,539,840 ~ 2.056 x 10^151 Key space: ~ 2.056 x 10^151