E-Signature Objective, Design & Consideration

<TODO: Finalize with the team>

Start with the use case. refer to the scope once to be clear.

Definitions:

E-Signature or an electronic signature is a way of signing documents digitally, without needing to print them. It’s sort of like an electronic version of a pen and paper signature or stamp, specific to a person or organization and is both secure and legally binding. In our context, E-Signature will mean cryptographically validatable signatures.
Qualified Certificate (EIDAS term) - a certificate in form of X.509 that allows the user's digital signature to be equal to a handwritten signature. It can be issued only according to legally accepted procedures.
Qualified Signature Creation Device (EIDAS term) - device that allows users to give signatures. Technically follows legally accepted procedure. There are different types:
- Physical token (ID card, Smart card, USB token)
- Remote token/EIDAS remote QSCD/Split key ( Cloud + App, Cloud + App + Secure element, Cloud + SIM card, Cloud + App + eSIM)
- As requirements, we can define this to be:
  - Defined in EIDAS QSCD list https://esignature.ec.europa.eu/efda/notification-tool/#/screen/browse/list/QSCD_SSCD
  - Certified by Common Criteria
  - Certified/Endorsed by FIDO
Signing Application - 3rd party or Government Application that implements the document signing.
- Standalone application (Desktop, Mobile App)
- Embedded application - embedded into another service, e.g web portal, online self-service, product
Onboarding - the process of issuing a Qualified Certificate and binding it to a Qualified Signature Creation Device, can involve different ways, subject to legislation:
- Face to face
- Online + authenticated with existing token
- Online re-onboarding only
- Full online
Signature Requestor - An application that has the artefact that needs the users signature.
Document/Artefact to be Signed - Data that needs to be signed by User. It can be
- a Document file (pdf, word, etc) owned/handled by User
- a Data file in an arbitrary format owned/handled by the user
- A Document or Data file handled by a 3rd party Service on behalf of user.

Scope:

Phase 1:

Limit the scope of work to the following

Ability to create and manage keys in remote QSCD.
- This is needed to support the server-side signing of documents. Mostly used by applications without much user involvement.
- Use cases like Payroll signing, agreement signing etc are handled using this API. Does not require an individual or would not interact with the ID building block.
Ability to create & sign using dynamic short-lived keys.
- This is needed to support the ID BB based signature. Mostly used by the end user to sign documents or by the applications on behalf of the end user and sign.
- Use cases like consent, tax filing, request for registration etc can be handled.
Support for the following signature formats:
- XAdES
- CAdES
- ASIC
- JWS
No administrative API’s are need to cater to this requirement. So administrative API’s will be left out of scope

All signatures are expected to be happening on the server.

The government signed document G2P – Priority
The end user signs the document. P2G - Priority
Business signing the document. B2B or B2C, G2B, B2G - last
Quantum resistance - Not in scope as of now.
Remote e-signature would be considered as the scope.

Objective:

The ability for anyone to sign
- One authentication based E-signature
  - OTP
  - Biometrics
  - PIN
- One Time Signature
  - WOTS+ - Not supported
  - XMSS - Not supported
- Long-term signature
  - Smart cards
  - Smart Phone.
- HD Signature
  - Smart Phone
Use ID BB to authorize and sign a document.
- Should be possible to sign with a standalone app, without ID BB.
Auditability
Validatable
Revoke certificate.
Highly secure.
Preservation of E-Signature
Non-Repudiation
Long-term validatable.
Inclusive
- Supports multiple social economic backgrounds.
Presentation
- Can we support multiple signature types and let verifiers provide presentation layers?

Assumptions:

Has a digital ekyc or authentication service.
- Registration/KYC should be possible to be performed online or face to face
- Should be possible to perform via phone call/SMS
Bulk signing is out of scope.
Collaboration in the signature is limited by the type of the document and the support of the document.
Countries are expected to have digital signature law’s that consider e-signatures as equivalent to handwritten signatures.
No support for printing the digital document and validating the signature.

Challenges:

Central service vs Distributed model
What if there is no eKyc/auth available?
Phone-based signature?
Online and/or Offline validation
Can we use JSON-LD signatures so we can validate a linked PDF or HTML or image etc.

Key principles:

Flow:

Sign using a cryptographic key and explain

How do we verify? explain here

How can we make it easy for everyone in the country to use it?

Kassy - preservation means the ability to use a digital signature and validate the same digital signature

Let us add one or some of the sample digital signatures.

https://tcab.eu/eidas-assessment/seal-preservation/

Differentiate validation vs creation of digital signatures.

Solution:

There should be levels of how strongly KYC is done and how good is the signature creation device
How do we take care of the machine signature? Is this in scope?

Sample Use cases: - Priority 1

Notes from Ramkumar:

Can we map a use case with the mother-child?

Govstack Building Block Cookbook

Consider the below as scenarios.

Use case 1: Signature of the resident on the consent form to share his details.

Actors:

Consent Building Block, Resident, Application, Agent, ID Building Block

Type:

C2G

Steps for approach online:

Agent opens up the consent form.
Describes the services to the resident.
Resident authenticates to the ID Building Block
The resident is redirected to the Application
The Application gets the necessary consent form and shows it to the agent/resident.
The resident chooses to sign the consent form with a button click.
The Application sends the consent form and the bearer token of the user to the e-signature building block API.
The e-signature building block validates (introspects RFC 7662) the bearer token with the ID building block.
Creates the key on the fly and timestamps & signs the document. (different types of signatures are allowed). The key is valid only for a short duration.
The e-signature building block sends back the signature in the requested format (XAdES, CAdES, ASIC, JWS)
The Application decides on the resident’s e-kyc details and sent back the certificate (X509v3) to the USB token.
1. The e-signature building block will use a certificate authority to get the certificate.

Alternate Onboarding:

The resident is provided with a smart card as part of the id enrollment.
The smart card has an e-signature certificate pre-burned into it.
The smart card is sent to the resident/picked up by the resident after proper verification.

Steps:

Agent opens up the consent form.
Describes the services to the resident.
Resident authenticates to the ID Building Block
The resident is redirected to the Application
The Application gets the necessary consent form and shows it to the agent/resident.
The resident chooses to sign the consent form with a button click.
The Application redirects to the e-signature building block.
The e-signature building block asks the resident to insert the USB token.
The e-signature building block interacts with the USB token and signs the document.
The e-signature building block sends back the signature in the requested format (XAdES, CAdES, ASIC, JWS) to the Application.
The Application decides to embed or attach the signature data.
The workflows building block sends the signature to the consent building block.
The Application shows the user that consent is signed and he can download it from a link given.

Use case 2: Payroll signature

Can we have the payroll statement signed before it's sent for the payment block?

Type:

G2B or B2B or B2G

Sequence Diagram:

Related use cases

Sign you invoice.
Sign an RFP
Sign a business agreement.

Use case 3: Signing and verifying a document owned by user using a desktop computer or mobile phone

<Description by Jürgen Niinre .

Type: C2G, G2C, G2B

Terms and Definitions

Prerequisites

The user has been onboarded, has been issued a Qualified Certificate and owns or controls a Qualified Signature Creation Device.

Signing user-owned document:

The user uses the Signing Application directly by choosing documents to be signed
The Signing Application will present the documents or data to be signed
The Signing Application will authenticate to e-signature BB, using an embedded token that allows for fixed e.g 10 requests/month
The Signing Application will create a signature with Qualified Signature Creation Device
- User is verified using PIN code and/or biometrics
- Signature and Certificate are sent to e-signature BB to be verified
e-signature BB will confirm certificate validity
e-signature BB will issue timestamp
e-signature BB will send back a signature with certificate validity and timestamp
Signing Application will save the signature, validity information and timestamp together with document, so that document with this embedded information can be validated later
The application will present results to user

Sequence Diagram:

Related use cases

Use case 4: Signing a consent form

Type:

Sequence Diagram:

Related use cases

Kassy use cases

Local signature - Cryptographic token
Distance signature - sign your own
Before you get a key you should get the kyc from the certificate authority.
Gtax generates the key and certificate to sign and then returns the application.

kassy - please update the use cases that you are aware of.
kassy - please share the links of the esignature services available in your country.
sasi - update India esign details.
muttalib - pls update more on this https://legalseba.com/digital-signature-in-bangladesh/
HR documents (employment contracts, privacy notices, non-disclosure agreements, benefits paperwork), contract management, e-invoices.
Need to explore more on this. https://ec.europa.eu/digital-building-blocks/wikis/display/DIGITAL/eSignature

Reference:

Introduction to cryptographic digital signature - https://www.youtube.com/watch?v=704dudhA7UI

India e-sign paper - https://cca.gov.in/sites/files/pdf/ACT/eSign-APIv2.0.pdf

India Other modes: Device-based.

Estonia eSignature mobile application - https://www.id.ee/en/article/ria-digidoc-mobile-application/

Estonia eSignature desktop application - https://www.id.ee/en/rubriik/using-digidoc4/

Estonia eSignature creation and verification libraries - https://www.id.ee/en/article/digidoc-libraries-overview/

Estonia eSignature timestamp service - https://www.skidsolutions.eu/en/services/time-stamping-service/

Estonia eSignature validity confirmation Service - https://www.skidsolutions.eu/en/services/validity-confirmation-services/

Estonia eSignature(container) format - bdoc-spec212-eng.pdf

Estonia eSignature certificate format - https://www.skidsolutions.eu/upload/files/SK-CPR-ESTEID2018-EN-v1_3_20220217.pdf

Estonia split key - https://cyber.ee/uploads/Split_Key_White_Paper_3506f03c34.pdf#:~:text=SplitKey is a technology bringing true cryptographic platforms,specialised hardware platforms%2C such as hardware smart-cards or

Estonian citizens can choose a suitable method for digital signing themselves. Nowadays, there are four common ways to do so:

An ID-card, which is a mandatory identity document for all Estonian citizens. The PINs required for electronic signing are issued to you in a security envelope with the card. In order to use your ID-card, you also need a card reader and ID-software.
A digital ID card: Estonian citizens can use their digital IDs in parallel with ID-cards while foreigners are issued e-resident’s digital IDs.
A mobile-ID is a SIM card-based solution for electronic authentication and digital signing with a mobile phone. Mobile-ID SIM cards are issued by mobile network operators.
A Smart-ID is a SIM-independent device-based solution for smartphones.