Help fight my ignorance on encryption

Factual Questions
21

[QUOTE=Kevbo]
To cite a classic example, that used when decrypting messages from the WW2 enigma encryption device:

The manual for the device suggested that to enhance security, messages should start with a nonsense word, “Sonnenschein” (sunshine) was given as an example. True to German genauigheit (exactingness) an ovewhelming majority of the enigma messages started with the word Sonnenschein.

In addition, most of the messages ended with the words “heil Hitler”. Thus it was only reqired to test a key on the first few, and last few letters of a message, and rather than analyzing for “Germaness” of the resulting plain text, these specific words could be checked for.
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Didn’t they get a break on the naval enigma (with its extra rotors) when they captured a codebook that detailed the kriegsmarine’s weather reporting codephrases. So they just had to take a look at the weather reports for a particular area to have an idea of what were the starting machine settings for the day?

22

They had all sorts of tricks. A favourite was to get the RAF to drop mines into a harbour. The harbour master would then transmit a message to the Kriegsmarine stating that the harbour had been mined. As Bletchley knew the map co-ordinates of the harbour (from captured maps), they had a clue as to the contents of the message.

IIRC, one particular radio operator in Germany always began his messages in the same way, too, making them easier to decrypt.