When the PT-109 American patrol boat, under the command of Lieutenant John F. Kennedy, was sunk by a Japanese destroyer, a message was received at an Australian wireless station in Playfair code:

A. KXJEY UREBE ZWEHE WRYTU HEYFS

B. KREHE GOYFI WTTTU OLKSY CAJPO

C. BOTEI ZONTX BYBNT GONEY CUZWR

D. GDSON SXBOU YWRHE BAAHY USEDQ

Meaning:

PT BOAT ONE OWE NINE LOST IN ACTION IN BLACKETT  

STRAIT TWO MILES SW MERESU COVE X CREW OF TWELVE  

X REQUEST ANY INFORMATION.

Explanation:

Playfair cipher  invented in 1854 by Charles Wheatstone was the first practical digraph substitution cipher. Lord Playfair promoted the use of the cipher, therefore it was named after him. Playfair cipher encrypts pairs of letters (digraphs) making it hard to break.  Frequency analysis can still be undertaken but requires much more cipher text in order to work. It requires no additional equipment to operate and is very fast therefore it is to protect information during war. It was used  by British forces in the Second Boer War and in World War I and during World War II by the Australians.  

When the PT-109 American patrol boat, under the command of Lieutenant John F. Kennedy, was sunk by a Japanese destroyer, a message was received at an Australian wireless station in the morning of the 2 of August 1943  in Playfair code:

KXJEY  UREBE  ZWEHE  WRYTU  HEYFS  

KREHE  GOYFI  WTTTU  OLKSY  CAJPO  

BOTEI  ZONTX  BYBWT  GONEY  CUZWR  

GDSON  SXBOU  YWRHE  BAAHY  USEDQ

Meaning:

PT BOAT ONE OWE NINE LOST IN ACTION IN BLACKETT  

STRAIT TWO MILES SW MERESU COVE X CREW OF TWELVE  

X REQUEST ANY INFORMATION.

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