What kind of Master Key/Keys Encryption is used for Nexus Sigchains Login?

[Gapcoin1]

I am curious to know as it's hard to find out from the source code where it's tied into!

[Gapcoin1]

From one of the Whitepapers

https://github.com/Nexusoft/GenesisWhitepaper/blob/master/main.tex

"Nexus hashing is built from two secure hashing algorithms: Skein and Keccak \cite{sha3announce}.
These two algorithms are combined to form a single SK-1024 (Skein-Keccak 1024 bit) hash.
There are three types of output lengths in Nexus hashing: SK-256, SK-512, and SK-1024.
Public keys are hashed with SK-256 to secure them from public knowledge until spent.
Transactions are hashed with SK-512 while SK-1024 is used for the proof-of-work hash."

That is part of the process............but what I am curious is how Nexus is secured while logging into the Sigchain...........What is the Encryption used to first key into the Sigchain