yeah, in southeastern europe it was viber, i think northeastern europe it was telegram, it's whatsapp here in portugal, my landlords and ladies all have asked to use it, even though we all have $10/month SMS prepaid accounts with vodafone and whatnot signal was actually the first, they merged out of redphone and some other thing i forget, some SMS type deal, they actually were the ones who pionered using SMS as auth right in the beginning, circa 2013, i had redphone on my sony xperia android back then so, yeah, you obviously were not there when it was all starting, circa 2012-2013, it was definitely signal first, and everyone else was riding on top of that, and it was open source originally, that's part of how it happened signal -> whatsapp -> telegram is the sequence i recall i was in balkan so maybe it looked a little different, they had viber, which also was big i think in west asia, ie india, pakistan, georgia, etc

yeah, that definitely was not the sequence of events signal started in about 2014-15 and their protocol was used by the rest of them, so-called "double ratchet" protocol, and you may also have heard of "OTR" messaging, that also came around the same time, it was out of the same school of cryptography development signal was born out of the merger of the FIRST SMS based auth service, and everything else uses that now, whatsapp, telegram, viber, they all use that, but it was invented by Redphone here's some history

Open Whisper Systems - Wikipedia

I think I was playing around it as well around that time. Even did couple of calls over their encrypted connection. Felt pretty 7331 haxx0r at the time. But it was lagging as hell. Probably would've gotten use to it if someone else would've used it also. But they were pretty unknown. I heard about them because we had some innovation hackathon at the place I worked then. One proposed project for the hackathon was encrypted chat app, and after searching, found the redphone. Another project was planning poker for software development teams.

I mispelled "chatsecure", was " textsecure" instead... whatsapp launched in 2009, and reached great popularity in the first years of smartphones here in italy. The facebook acquisition happened in 2014. Then has been "upgraded" with the signal protocol by the collaboration with the signal guys in later years.

nono, whatsapp was far earlier, remember people buying esplicitely android phones and not nokia symbian to have whatsapp working better