Document Signing

EidKit uses the nonRepudiation key on the Romanian CEI chip to produce a qualified ECDSA-SHA384 signature over a document hash. This enables PAdES/eIDAS-compatible PDF signing.

How it works

1. Your app computes a SHA-384 hash of the document byte range to be signed
2. The user taps the card and enters their 6-digit signing PIN
3. The chip signs the hash using the nonRepudiation key (key ref 0x8E in the GenPKI applet)
4. EidKit returns the raw 96-byte r||s ECDSA signature and the DER X.509 certificate

Sign a document

Android (Kotlin)

// 1. Compute the SHA-384 hash of your document content
val hash = MessageDigest.getInstance("SHA-384").digest(documentBytes)
// hash.size == 48

// 2. Execute the signing session
val result = EidKit.signer(can = userEnteredCan)
    .sign(hash, signingPin = userEnteredSigningPin)
    .execute(isoDep)

// result.signature    — 96-byte raw ECDSA-SHA384 r||s
// result.certificate  — DER-encoded X.509 CE8E certificate

iOS (Swift)

import CryptoKit

// 1. Compute the SHA-384 hash of your document content
let hash = Data(SHA384.hash(data: documentBytes))
// hash.count == 48

// 2. Execute the signing session
let result = try await EidKit.signer(can: userEnteredCan)
    .sign(hash: hash, signingPin: userEnteredSigningPin)
    .execute()

// result.signature    — 96-byte raw ECDSA-SHA384 r||s
// result.certificate  — DER-encoded X.509 CE8E certificate

Embedding the signature in a PDF

SignResult.signature is a raw r||s value. To embed it in a PDF (PAdES/eIDAS), it must be wrapped in a CMS/PKCS#7 SignedData structure together with the certificate.

Options:

• EidKit signing service — set EidKitConfig.signingServiceUrl to delegate CMS wrapping, timestamping, and LTV to the EidKit backend (or your own on-premise instance)
• DIY — use Apache PDFBox (Android) or PDFKit/BouncyCastle to build the CMS structure yourself from result.signature and result.certificate

Progress events

Android (Kotlin)

EidKit.signer(can = userEnteredCan)
    .sign(hash, signingPin = userEnteredSigningPin)
    .executeFlow(isoDep)
    .collect { event ->
        when (event) {
            is SignEvent.PaceEstablished -> showStep("Secure channel opened")
            is SignEvent.PinVerified     -> showStep("PIN accepted")
            is SignEvent.Done            -> showResult(event.result)
        }
    }

iOS (Swift)

let result = try await EidKit.signer(can: userEnteredCan)
    .sign(hash: hash, signingPin: userEnteredSigningPin)
    .execute { event in
        switch event {
        case .paceEstablished: showStep("Secure channel opened")
        case .pinVerified:     showStep("PIN accepted")
        }
    }

Signing PIN

The signing PIN is 6 digits — different from the 4-digit authentication PIN used for KYC. The Romanian CEI allows only 3 incorrect signing PIN attempts before the signing key is permanently blocked.