Canon EOS 550D Instruction Manual page 108

Custom Function Settings*
0: Disable
1: Enable
Data for verifying whether the image is original or not is appended to the
image automatically. When the shooting information of an image
appended with the verification data is dispbayed (p.173), the <_> icon
will appear.
To verify whether the image is original, the Original Data Security Kit
OSK-E3 (sold separately) is required.
The images are not Compatibl e with the image encryptiontdecryption ......
features of Origina! Data Security Kit OSK-E3,
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