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Naval Cypher #4
Posted by wr on January 10, 2019, 8:11:58
The British knew that naval cypher #4 had been broken and was being read by the Germans by October 1942 and possibly much earlier. Does anybody know (with a source) as to which month the British became aware of this breach.
PS The Germans had passed onto to Japanese by december 1942 the fact that they were reading cypher #4. The British were also aware of this .
NB Naval cypher #4 continued to be used until the latter months of 1943, probably for counter intelligence reasons.
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