Abstract

CashID is an open protocol that allows secure authentication based on the public key cryptography infrastructure that is currently present in the Bitcoin Cash ecosystem. By authentication we mean to prove to a service provider that we control a specific Bitcoin Cash address by signing a challenge request that links the users address and optional metadata to a task or session with the service provider.

Motivation

Secure authentication and safe storage of credentials is useful for many things, and with added metadata we enable the following usecases:

Register to a service as a 1-step process.
Register to a service automatically as part of a payment.
Authenticate to a service to login without a password.
Authenticate to a service to act as 2FA complementing existing passwords.
Provide access control to locks based on payment.

Specification

Workflow

When a user needs to access a restricted area (physically or digitally), they are given a challenge request in the form of the following data:

cashid:domain.tld/command?x=[nonce]

This challenge request can either be transmitted via a QR code, NFC or by any other implementation specific transmission method.

Request structure

cashid://domain.tld/command?x=[nonce]&a=[addr]&r=[scope]&o=[scope]

Parameters

x= nonce a= bitcoin address r= required metadata o= optional metadata

Metadata

Identification is represented by the letter i followed by a list of numbers corresponding to the following table.

Number	Name	Data type	Description
1	Name	String	The first / given name
2	Last name	String	The last / family name
3	Middle name	String	Extra names
4	Nickname	String	A nickname or username
5	Picture	String	URL to a profile picture, or Base64 encoded image
6	Age	Integer	The number of years the person has lived
7	Gender	???	The sex of the person
8	Birthdate	Date	The date of birth... what format?
9	Identification	string	National identification number

Location is represented by the letter l followed by a list of numbers corresponding to the following table.

Number	Name	Data type	Description
1	Country	String	Name of the nation
2	State	String	Name of the state or province
3	City	String	Name of the city
4	District	String	Name of the district, region or neighborhood
5	Postal Code	String	....
6	Street Name	String	Name of the street, without the street number
7	Street Number	String	The street number
8	Apartment	String	Building or apartment number
9	GPS	String	Comma-separated list of longitude and latitude

Contact information is represented by the letter c followed by a list of numbers corresponding to the following table.

Number	Name	Data type	Description
1	Email	String	Email address
2	IM	String	Instant Messenger protocol handle
3	Social	string	Social media service handle
4	Mobile Phonenumber	string	Personal cellphone number
5	Home Phonenumber	string	Residence phone number
6	Work Phonenumber	string	Work phone number

Rationale

Passwords is an inherently flawed concept (based on sharing secrets) that is increasingly getting hidden away from the users by means of password managers, 'remember me' and single-signon features. Public key cryptography provides a more secure method for authentication where the users secret is never shared.

The problem with public key infrastructure is that managing private keys securely is complex, but this complexity is now being addressed in the cryptocurrency ecosystem which makes it possible to safely implement a better authentication system.

Resources

Supply a functional regexp!

1: that parses the request string
2: that parses the metadata scope

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