What matters is how similar the precise combination of visual elements are in the two logos.
Yes, it is possible that they were created independently. However, after looking at the "evidence" provided by Daiz, it seems more likely that an anonymous channer borrowed the design without crediting it.
"I just got back from the store. I picked up some bananas while I was there."
Both sentences say the same thing. No, they are not completely the same, but neither are the logos in question.
If you want to talk about precise combinations of visual elements, there are LOTS of differences.
Look closely at the logos. The Tox logo makes the person more like a keyhole. The Secure Chat logo uses something more like a natural human silhouette. The ratios of the arc to square are different. The spacing is different. There's a bunch of differences. Frankly, my eye appreciates the the layout and design of the Secure Chat logo... the weights of the Tox logo are a little off... I DO really like the keyhole/person combo, though! So each design has its merits.
The only similarities are the padlock, the chat bubble, and the person.
Just like how in my textual sentences the only similarities are "store", "multiple bananas", and "at some point today".
The point is, the two sentences, one textual and the other visual, both "say the same thing" and are made up of "the same concepts" and "predefined elements of language"... and neither should be considered plagiarism or even that unique to warrant talking about originality...
1.) Using a padlock to represent computer security.
2.) Using a cartoon chat bubble to represent a way to chat on your computer.
3.) Using a little oval on top of a bigger oval to represent a person.
Is it really that much of a stretch to combine the three? I would think that this concept would be pretty standard output from someone with even a moderate amount of visual communication skills.
It's a rather simple visual sentence and I can easily imagine quite a few people having come up with this concept.
Please realize that both logos are built on top of an already existing visual language and that neither of you are really all that original to begin with.