Doesn't look like any flags/bits are set in sysprocesses, monProcess nor monProcessLookup.
If you enable auditing of logins it looks like you can get the desired info from the sysaudits_XX.extrainfo column.
I pulled the following from sysaudits_XX for 2 of my test connections ... one using 'isql', one using 'isql/-X':
isql: "..., <ip_addr>, network password no encryption; ..."
isql/-X: "..., <ip_addr>, network password rsa encryption with nonce; ..."