SIGNAL SERVICE, WAR DEPARTMENT, WASHINGTON D.C.
February 1931, the 27th,
My dear students,
Your analysis of the B-211 operation is complete. In
the end you have created a "pencil and paper analog". I will give you
the opportunity to test it.
I encrypted a message using the machine. I ask you to
decipher it. I remind you the structure of the secrets elements (keyboard and
half-rotors) and also gives you the internal key and the message key.
If you succeed in decryption, you will have proven
your complete understanding of the machine.
Good luck !
W.F. FRIEDMAN
CHIEF CRYPTANALIST
Keyboard Grid:
LMYFX
OJBRS
PUGCW
KNTDQ
IHVEA
Plugboards:
AEIOU:LNRST:
Vowel Rotor:
Consonnant Rotor:
ABCDEFGHIK
ABCDEFGHIK
01243 23104
32410 34201
12304 12043
43021 23140
23410 01432
04132 12034
34021 40321
10243 01423
40132 34210
21304 40312
Internal Key
AEUIO:TSNRL
Wheel 23 A.CDEF..I.LM.....STUVXY
Wheel 21 .BC...GHI..M.OP....UV
Wheel 19 ..C.E.GH....N.PQ..T
Wheel 17 AB..EF.HI.LM.....
Remark: When the rotors are all set at “A” against the
bench mark (i.e. the apparent setting is AAAA), the effective setting will be
GFFE.
Message key:
HAGLIN
The cryptogram:
WGLDN GVDAI TXXCS PMODV KXKRO UCAKN KAFRW JMHFU SXELK
OONMT
WXGJE FIYAA HLNOY RONOU BPRIO MCPWX DKHXE DWBXE XIOSD FIAFS
QRBXJ DVODA YGXBK RWSAY OEHTE DJWQD GOWPH BOHFI NWHSA YVEGS
RDBED OOHFE BCWFC XJKVM PNITV IDTBC SLORD MNSYQ SKMHJ BRQYW
DJOXX BOAVW OHWMA QYKXB AITGA BROPT OTFKN IQHUE PLDAQ ABBGK
CDGTP KOQIR JPLCI JGDMD CUPUT F