How to decrypt PKCS#8 encrpyted private key in javascript

Question

I am working on ServiceNow - BOX integration using rest API. for generating access tokens, I need to generate a JWT.

I need to have a private key to sign that JWT.

They have provided the private key but it is in an encrypted format.

-----BEGIN ENCRYPTED PRIVATE KEY-----
*******Key here********** 
-----END ENCRYPTED PRIVATE KEY-----

I have also been provided with a pass code to decrypt it.

I am not sure how to decrypt above private key in ServiceNow.

Please help me in getting this done in javascript pure implementation.

Thanks,

Ali

Adding the privateKey and passphrase in the front end is a bad idea. I suggest you use your backend as a middle layer and send request to servicenow-box from the backend. — nightgaunt, Nov 30 '18 at 06:07
Yes. I am not using these keys in frond end. These will be processed at server side in servicenow. How can I get decrypted private key with pure javascript ? — Ahmed Ali, Nov 30 '18 at 06:16
Which backend technology are you using? To be more precise, which backed tech servicenow uses? — nightgaunt, Nov 30 '18 at 06:39
ServiceNow uses javascript in backend as well. Recently It upgraded to ECMAScript5 engine. I need to have javascript code for decryption. I can have CryptoJS in servicenow for signing the jwt with rs256. But just not sure about how to have decrypted key from above encrypted form with the passcode. — Ahmed Ali, Nov 30 '18 at 06:47

Ellery · Accepted Answer · 2018-11-30T08:36:15.690

From what you posted above it looks like you are receiving the key in PKCS#8 format https://en.wikipedia.org/wiki/PKCS_8

From some quick googling looks like this library may be your best bet for extracting this value. https://github.com/kjur/jsrsasign

Here is code in that library that decodes this:

Here they are using in a unit test. Probably similar how you will need to call.

1 Answers1