I use Aegis as my 2fa. Today on new token creation I observed that there’s hash function set to SHA-1, later checked all my tokens and the result is same type of encryption used for all. So I have edited all my tokens to SHA-256 as a result my totp doesn’t authenticate. Do I have to rescan my tokens for updating to SHA-256 or it doesn’t work like that?
Security: SHA-1 < SHA-256 < SHA-512
Speed: SHA-1 > SHA-256 > SHA-512
My doubts are: Why can’t we use SHA-256? Is it because TOTP requires less time so faster one(SHA-1) is chosen? Can we use SHA-256 for TOTPs?
SHA1 was the official standard when TOTP started being widely deployed. I wouldn’t worry. If you look at how the hash function is actually used in the TOTP algorithm, it would be very hard to exploit SHA-1’s vulnerability to finding free collisions. It’s much more likely that either the server or the client app gets pwned somehow.