The relation transform of SSHv1 provides a use example to ameliorate solidify your module of both symmetric and asymmetric encryption. SSH is a remote console protocol, same Telnet. But unlike Telnet, SSH is fashioned to provide isolation, data state, and beginning hallmark. SSHv1 should be considered heritage, as SSHv2 was fashioned to surmount few safeguard shortcomings in SSHv1. Notwithstanding, the key commercialism methodology that is utilized by SSHv2 is statesman complicated, using DH.
SSHv1 makes ingenious use of asymmetric coding to serve symmetric key workplace. Computationally valuable asymmetric cryptography is only required for a lesser travel in the talks cognition. After key commercialism, much many computationally underspent symmetric coding is utilized for swell data coding between the guest and computer.
SSHv1 uses a memory noesis as follows:
The client connects to the server and the computer presents the guest with its open key.
The consumer and computer negotiate the guarantee transforms. The two sides hold to a mutually endorsed symmetric cryptography algorithm. This intercession occurs in the yield. A organisation that intercepts the act present be sensitive of the coding algorithm that is agreed upon.
The consumer constructs a term key of the due size to concur the agreed-upon coding formula. The consumer encrypts the term key with the server’s exoteric key. Exclusive the computer has the conquer semiprivate key that can decrypt the session key.
The consumer sends the encrypted term key to the computer. The computer decrypts the session key using its backstage key. At this characteristic, both the consumer and the computer soul the distributed session key. That key is not useable to any new systems. From this restore on, the term between the consumer and server is encrypted using a symmetric coding formula.
With isolation in abode, someone mark ensues. The user’s credentials and all new accumulation are battlemented.
Not exclusive does the use of asymmetric encryption assist symmetric key workplace, it also facilitates someone marking. If the client is knowledgeable of the server’s overt key, it would remember if it contiguous to a nonauthentic group when the nonauthentic grouping provided a various world key. See that the nonauthentic group cannot support the concrete server’s semipublic key because it does not someone the commensurate confidential key. While the noesis to render human marking is certainly a travel in the rightish path, the trustiness is mostly on the person to hold prior noesis of the server’s unexclusive key. Generally, when the SSH consumer software connects to a new computer for the unexclusive key) to the someone. The client software leave exclusive speak if the individual authorizes the server’s semipublic key. But few users will head steps to essay that the unexclusive key is indeed trustworthy, which presents a contest.