Tuesday, April 27, 2021

Beware of Signal Recompressing Images and Videos

Jeffrey Paul (Hacker News):

Signal took that 4000x2667 JPEG image comprising precisely 3,916,886 bytes, encrypted it, and transmitted it to my friend. She received a different 4000x2667 JPEG image comprising 784,524 bytes: 80% smaller.


Did you know that the everyday, normal-sized (<4MB) images you send via Signal are being silently altered in transit to look like dogshit?


If they feel it’s absolutely necessary for them to do this to continue to exist as a free service: they should be much, much clearer about the fact that this is going to happen, at the time of recompression, and permit you to opt out of sending an altered file. As well as, just, you know, not touching images that are already reasonably sized.

See also: The silliness of iCloud Photo Sharing quality degradation.


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