Electronic signatures Ferenc Suba LLM MA Chairman of

Electronic signatures Ferenc Suba LLM, MA Chairman of the Board, CERT-Hungary, Theodore Puskás Foundation Vice-Chair of the Management Board, European Network and Information Security Agency

How does it work? Cryptography: encode and decode a text with a key or keys Same key for both encryption and decoding in the symmetrical cryptography Different key (public and private keys) for coding and for decoding in the asymmetrical cryptography. The two keys are complimentary. Hash Function is an algorithm with creates a short message from the original text, a fingerprint. You are not able to create the original message if you know the hash created from it. Electronic signature is one of the asymmetrical ways of cryptography. It is used by the signer to sign the fingerprint of the document and this signed "fingerprint" is unique to both the document and the signer.

How does it work? SENDING: 1. 2. 3. 4. Sender creates hash message from the original plaintext (hash function, fingerprint). Sender encrypts hash message with his own private key, in this way he proves that he was the only one to send such a message. Sender encrypts the plain text with receivers public key. The sender is sure the message can be decrypted/read only by the receiver. Sender sends both encrypted hash message and ciphertext by e-mail to the receiver.

How does it work? RECEIVING 1. 2. 3. 4. Receiver decrypts the ciphertext with his own private key. He gets the original message. Receiver creates hash message from the original plaintext (hash function). Receiver decrypts the received encrypted hash message by public key of the sender. Finally, the receiver compares the two hash messages. If those two are the same, everything is all right and the message was not modified. If they are not the same, somebody had to modify the message during its journey through the Internet.

PKI Public Key Infrastructure (PKI) is the basis for e-signatures PKI provides each user with a Private Key and a Public Key The Private Key not shared, used only by the signer The Public Key openly available, used by those that need to validate the signer’s digital signature. PKI’s components: Certificate Authority (CA), end-user software, , tools for managing, renewing, and revoking keys and certificates.

CA, CRL, RA Certification authorities: trusted offices which administer keys. CA issues proof which proves identity of the user and his public key (= certificate). CRL: Certificate Revocation List - the place where a CA stores the IDs of all the Digital Certificates that have been revoked. CA's form a hierarchy. The top of this hierarchy is the root CA. Registration Authority – An RA does the required identification for certain certificate data, which is then passed to the CA for issuing the Digital Certificate.

Certificates can contain: • public key and name of the key, • date of expiration, • name of the certification authority who issued the certificate, • serial number (necessary for the evidence), • digital signature of the certificate issuer. Certificates with different level of trustworthiness. Qualified Certificate : Certificate issued by a CA with national accreditation Qualified Electronic Signature: e. Signature based on a Qualified Certificate.

Legal aspects What is a signature? Proof of authenticity Sign of willingness to undertake an obligation When is a contract binding? Meeting of the minds The objective vs. the subjective The formalistic approach Are electronic contracts binding? The ”electronic” dimension

Electronic contracts A binding contract means an enforceable contract? Not all contracts are enforceable The legal vs. the economic view Can you prove that a contracts is binding? The burden of proof before the Courts What evidence can be submitted? Rules concerning weight of evidence Electronic contracts are binding!

Principles (techno + legal) Properties of a digital signature Authenticity Integrity Confidentiality Non-repudiation

EU Directive on electronic signatures 1999/93/EC Directive on a community framework for electronic signatures Scope Regulation of certification service providers and their liability Not: The formation and legal validity of contracts Liability of certificatio service providers and Not of users Technology neutral legislation

Definitions Electronic signature ”Advanced” electronic signature Signature-creation device ”Secure” signature-creation device Certificate ”Advanced” certificate Signature-creation data Signature-verification data Certification-service-provider

Market access Provision of certification service shall not be subject to prior authorization Monitoring by local authorities is required and allowed EU co-operation on standards Internal promotion of the use of digital signatures through public sector Internal market principles with respect to the certification service market.

Legal effects of electronic signatures Advanced electronic signatures based on qualified certificates Satisfy legal requirements of a signature in relation to data in electronic form in the same manner as a hand-written signature satifies those requirements in relation to paper-based data Are admissable as evidence in court proceedings Other electronic signatures may not be discriminated against

Liability of certification service provider The issuer of a qualified certificate is liable for damages caused by reliance on The accuracy of the information in the certificate The assurance of the identity of the holder of the certificate The complementarity of the public and the private key Reversed burden of proof Liability for failed registration of revocation Limits on the use of the certificate and on value of transaction

Data retention According to Directive on data protection and Directive 97/66/EC: Traffic data must be erased or made anonymous immediately after the telecommunications service is provided, unless they are necessary for billing purposes. Only ”appropriate, neccesary and appropriate” restrictions are permitted.

Anonymous use and access Privacy vs. Non-accountability Re-mailers, Internet cafés, Dynamic IP-numbers Encryption technologies Art. 29 Data protection working party: Anonymity is THE question! The Bonn declaration (July 1997): Off-line rights must also apply in on-line

The governance of PKI Ministry: regulation (act, ministerial decrees) National Communications Authority: root CA, accreditation and controll of CA’s Standardisation Bodies: standards Alliance of CA’s: best practice Chamber of a regulated profession: rules for PKI related activities (e. g. Archiving for lawyers)

PKI services Time stamping Digital archiving Digital recognition of delivery Electronic Invoice Digital transformation (turning paper into digital)

Use of PKI today - e. Government mostly - Tax declaration - Company Registration - Excluded from: - Marriage - Real estate

EU picture - Diverging rules (recognition of foreign certificates, accreditation of providers of certification services) - High standards, high costs - Other “secure” signature methods: risk of unenforceable or voidable contract - Nov. 28 2008: Action Plan on e-signatures and eidentification (European Commission) - new ‘e-barriers’ to cross-border markets - to achieve interoperable e-signatures and eidentification

Thank you for your attention! ferenc. suba@cert-hungary. hu PTA CERT-Hungary www. cert-hungary. hu Theodore Puskás Foundation www. neti. hu ENISA www. enisa. europa. eu

Questions What is the public key, private key, hashing? What is the CA, root CA? What is the legal effect of a digital signature? Can you use e-signature in marriage?