I only know how it works in Gun. But basically, you generate a secret based upon one of the person’s keys. Then the other person can decrypt it with one of their other keys. 

But in Gun, each user has 4 keys. pub, private, epub, epriv. The epub and epriv are used in the secrets. 

https://github.com/amark/gun/wiki/SEA#example---public-key


thrown

247bf84fda

I'm not familiar with the term "shared secret pattern." The inspiration was bip47.