cbc vs gcm vs ... for my app?

currently ive get ecb 256 bit already implemented and working well, but i want an extra layer of privacy. if you had to send your ssn or credit card number over a vulnerable network, would you be more comfortable encrypting it with cbc or gcm?

@Condor ive heard gcm is a bit faster than cbc but i may be confused. my app has a public key built into it and encrypts the aes key then sends it to the server, so speed isnt a high priority, however ive heard how 256 are so hard to crack anyway that anything more than cbc isnt worth it.

@Condor would the speed difference even be noticeable? i mean it would have to be a pretty significant difference. all the app currently does is send a lot of <1kb json messages. i suppose the most data a client would send to the server thats encrypted would be a profile picture.

@Condor can you name any mobile devices which support this? i think samsung uses gcm a lot but im not sure. i want this app to be on ios and android so id want the best of both worlds

@Condor all i could find for android is this: https://software.intel.com/en-us/...

apparently, iphones have had it since 2013, so ill probably use whichever the iphones are best with.

@Condor there's no hardware support for 256 bit you mean?

@Condor i believe bit size does matter. i think iphones didnt offer hardware support for rsa 2048 bit and larger on their 5s model. either way thanks for the help but at the time ill probably just use cbc or maybe even ctr, and add the acceleration later if necessary.

@Condor Not me but @perfectasshole

@Condor Gotta go to work in less than half an hour 😭

@Condor Nono haha, going to work at 8. Work starts at 9 :)