It’s been a few years since I read anything involving crypto. I’ve come across this scheme and I wonder how secure it is:
Alice generates an RSA keypair (we assume Alice is using proper random numbers).
Alice sends the public key as plain text to Bob.
Bob generates a 3DES session key: BA.
Bob sends BA encrypted with Alice’s public key, together with a checksum of BA.
Alice receives and decrypts BA using its private key.
All following sensitive data is encrypted with BA and integrity is checked via the checksum.
When the checksum fails communication is aborted and Alice generates a new keypair.
What are the potential (or very real) problems with this scheme?