I always forget the -b option which allows changing the size of the key…. so Im putting this down here for future reference.
ssh-keygen -t rsa -b 2048
You can use dsa instead of the rsa after the -t to generate a DSA key. The number after the -b specifies the key bits. DSA is limited to 1024, whereas RSA isn’t. standard is 1024 if you don’t include the -b argument.