Any message sent after negotiating encryption must contain a MAC so that the other party can verify the integrity of the package. The MAC is calculated from the symmetrical common secret key, the message package number and the actual content of the messages. In 1998, SSH 1.5 described a vulnerability that allowed unauthorized insertion of content into an encrypted SSH stream due to insufficient CRC-32 data protection used in this version of the protocol.   An update known as the SSH Compensation Attack Detector has been introduced in most implementations. Many of these updated implementations contained a new vulnerability to digital overflow that allowed attackers to run any code with the permissions of the SSH amentmon, usually root. Thus, the SSH-Handshake establishes a secure connection between customers and servers. The basis of this procedure for the classic Diffie-Hellman is as follows: We propose an analysis of the widespread SSH key exchange mechanism. We use the SSH key exchange design to perform our analysis in a modular way. First, a common secret key is called via a Diffie-Hellman key exchange. Then, a transformation is applied to recover the application keys used by the later SSH phases.
We define models according to established paradigms that illustrate the security of different types of keys. To date, there has been no formal analysis of the SSH key exchange protocol. We provide modular security evidence for common application and SSH keys. We show that the common secret key exchanged by SSH is not identifiable, but that the applied transformation provides indissoluble application keys. Our proofs use random oracles to model the hash function used in SSH. This type of encryption scheme is often referred to as «shared secret» or «secret key» encryption. As a general rule, there is only one key used for all operations or a pair of keys where the relationship is easy to determine and where it is trivial to deduct the opposite key. SSH or Secure Shell is a cryptographic network protocol for the secure operation of network services on an unsecured network.
 Typical applications are remote control line, connection and remote commands, but each network service can be secured with SSH. As soon as the customer receives a SSH_MSG_KEX_ECDH_REPLY, he has everything it takes to calculate the secret K and the H exchange. In December 1995, Ylanen founded SSH Communications Security to commercialize and develop SSH. The original version of the SSH software used several pieces of free software, such as GNU libgmp, but later versions of SSH Communications Security became increasingly proprietary software.