Warning: I am a total JWT newb and trying to figure it all out.

First...what I understand: JWT contains three segments separated by . The first part can be base64 decoded to get "something" where I can validate the claims in the 2nd (and 3rd?) segment.

I am able to get the id_token back and can separate each segment into its respective JSON object...but thats not secure at all :)

I took a look at this https://github.com/firebase/php-jwt but I am unsure what KEY I need to supply to decode the JWT (I know I can decode the first segment and get the kid used for the JWT but when I have that specific key object...I'm not sure what to pass to firebase to decode it? https://login.microsoftonline.com/fabrikamb2c.onmicrosoft.com/discovery/v2.0/keys?p=b2c_1_sign_in

Please excuse my horrible understanding of JWT :/

EDIT: More Info

Using this ID TOKEN: eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6IklkVG9rZW5TaWduaW5nS2V5Q29udGFpbmVyIn0. eyJleHAiOjE0NDIzNjAwMzQsIm5iZiI6MTQ0MjM1NjQzNCwidmVyIjoiMS4wIiwiaXNzIjoiaHR0cHM6Ly9s b2dpbi5taWNyb3NvZnRvbmxpbmUuY29tLzc3NTUyN2ZmLTlhMzctNDMwNy04YjNkLWNjMzExZjU4ZDkyNS92 Mi4wLyIsImFjciI6ImIyY18xX3NpZ25faW5fc3RvY2siLCJzdWIiOiJOb3Qgc3VwcG9ydGVkIGN1cnJlbnRs eS4gVXNlIG9pZCBjbGFpbS4iLCJhdWQiOiI5MGMwZmU2My1iY2YyLTQ0ZDUtOGZiNy1iOGJiYzBiMjlkYzYi LCJpYXQiOjE0NDIzNTY0MzQsImF1dGhfdGltZSI6MTQ0MjM1NjQzNCwiaWRwIjoiZmFjZWJvb2suY29tIn0. h-uiKcrT882pSKUtWCpj-_3b3vPs3bOWsESAhPMrL-iIIacKc6_uZrWxaWvIYkLra5czBcGKWrYwrAC8ZvQe DJWZ50WXQrZYODEW1OUwzaD_I1f1HE0c2uvaWdGXBpDEVdsD3ExKaFlKGjFR2V7F-fPThkVDdKmkUDQX3bVc yyj2V2nlCQ9jd7aGnokTPfLfpOjuIrTsAdPcGpe5hfSEuwYDmqOJjGs9Jp1f-eSNEiCDQOaTBSvr479L5ptP XWeQZyX2SypN05Rjr05bjZh3j70ZUimiocfJzjibeoDCaQTz907yAg91WYuFOrQxb-5BaUoR7K-O7vxr2M-_ CQhoFA

I can decode the header segment eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6IklkVG9rZW5TaWduaW5nS2V5Q29udGFpbmVyIn0 to {"typ":"JWT","alg":"RS256","kid":"IdTokenSigningKeyContainer"}

then looking at https://login.microsoftonline.com/fabrikamb2c.onmicrosoft.com/discovery/v2.0/keys?p=b2c_1_sign_in

I know that this key object was used

{"kid":"IdTokenSigningKeyContainer","use":"sig","kty":"RSA","e":"AQAB","n":"tLDZVZ2Eq_DFwNp24yeSq_Ha0MYbYOJs_WXIgVxQGabu5cZ9561OUtYWdB6xXXZLaZxFG02P5U2rC_CT1r0lPfC_KHYrviJ5Y_Ekif7iFV_1omLAiRksQziwA1i-hND32N5kxwEGNmZViVjWMBZ43wbIdWss4IMhrJy1WNQ07Fqp1Ee6o7QM1hTBve7bbkJkUAfjtC7mwIWqZdWoYIWBTZRXvhMgs_Aeb_pnDekosqDoWQ5aMklk3NvaaBBESqlRAJZUUf5WDFoJh7yRELOFF4lWJxtArTEiQPWVTX6PCs0klVPU6SRQqrtc4kKLCp1AC5EJqPYRGiEJpSz2nUhmAQ"}

so...what value for the key would I pass to firebase?