dropbear has the goal of being small and light on ressources while still providing featurefull ssh support.
tinyssh is small because it only implements a tiny subset of SSH that is needed for secure basic SSH connections. It only includes few crypto primitives excluding even RSA.
There is considerable overlap in the two and you can reach something similar to tinyssh by compiling dropbear with only few select features, but tinyssh aims to be as secure and attack surface minimized as possible out of the box.
Another notable difference:
> no dynamic memory allocation - TinySSH has all memory statically allocated (less than 1MB)
tinyssh is small because it only implements a tiny subset of SSH that is needed for secure basic SSH connections. It only includes few crypto primitives excluding even RSA.
There is considerable overlap in the two and you can reach something similar to tinyssh by compiling dropbear with only few select features, but tinyssh aims to be as secure and attack surface minimized as possible out of the box.
Another notable difference:
> no dynamic memory allocation - TinySSH has all memory statically allocated (less than 1MB)