The objective of this post is to discuss the feasibility of splitting credentials into multiple machines.
Why to Split Key
- The motivation is to enhance the difficulty for the attackers to steal the key. The attackers would need to compromise several machines together
How to Split Key
-  RSA
Feasibility of Splitting Key to Protect Security
- Though the secrets are separated, the rebuilding process must occur, by necessity, on a single machine which obtains, at some point, the secret itself. In particular, if you do the reassembly on a machine which is evil (i.e., which is under the control of an attacker through some malware), then the attacker learns the SSH private key. 
- It is not feasible to defense covert channel attack through splitting credentials to multiple machines.
 Is there a way to split up my SSH Key using Shamir’s Secret Sharing?, in StackExchange