II think bit message uses ECIES. I believe it's secure as long as you perform your key exchange ok and you're using a secure symmetric cryptography (I might be wrong). and I think ( but I don't know exactly what your program does) that you are using the same sort of ideas. You would probably be better off just implementing ECIES though.
I don't think your OP explained your system in enough detail so it may have been misunderstood. Also bear in mind that I'm quite often wrong about stuff.
I don't think your OP explained your system in enough detail so it may have been misunderstood. Also bear in mind that I'm quite often wrong about stuff.
I am using ECIES, I think. I would need a more experienced cryptographer to examine the code to make sure, but it's fairly straightforward. The shared secret gets exchanged securely using the same discrete logarithm problem. The shared secret then is plugged into a key derivation function which is used to make a cipher and an hmac for evaluating the checksum. The cipher then is used for encrypting and decrypting the message. And the checksum is checked to make sure the message arrived un-modified. That's how ECIES works, I think. That's at least what I tried to implement.