(5 ILCS 175/5-105)
    Sec. 5-105. Definitions.
    "Asymmetric cryptosystem" means a computer-based system capable of generating and using a key pair consisting of a private key for creating a digital signature and a public key to verify the digital signature.
    "Certificate" means a record that at a minimum: (a) identifies the certification authority issuing it; (b) names or otherwise identifies its subscriber or a device or electronic agent under the control of the subscriber; (c) contains a public key that corresponds to a private key under the control of the subscriber; (d) specifies its operational period; and (e) is digitally signed by the certification authority issuing it.
    "Certification authority" means a person who authorizes and causes the issuance of a certificate.
    "Certification practice statement" is a statement published by a certification authority that specifies the policies or practices that the certification authority employs in issuing, managing, suspending, and revoking certificates and providing access to them.
    "Correspond", with reference to keys, means to belong to the same key pair.
    "Digital signature" means a type of electronic signature created by transforming an electronic record using a message digest function and encrypting the resulting transformation with an asymmetric cryptosystem using the signer's private key such that any person having the initial untransformed electronic record, the encrypted transformation, and the signer's corresponding public key can accurately determine whether the transformation was created using the private key that corresponds to the signer's public key and whether the initial electronic record has been altered since the transformation was made. A digital signature is a security procedure.
    "Electronic" includes electrical, digital, magnetic, optical, electromagnetic, or any other form of technology that entails capabilities similar to these technologies.
    "Electronic record" means a record generated, communicated, received, or stored by electronic means for use in an information system or for transmission from one information system to another.
    "Electronic signature" means a signature in electronic form attached to or logically associated with an electronic record.
    "Information" includes data, text, images, sound, codes, computer programs, software, databases, and the like.
    "Key pair" means, in an asymmetric cryptosystem, 2 mathematically related keys, referred to as a private key and a public key, having the properties that (i) one key (the private key) can encrypt a message that only the other key (the public key) can decrypt, and (ii) even knowing one key (the public key), it is computationally unfeasible to discover the other key (the private key).
    "Message digest function" means an algorithm that maps or translates the sequence of bits comprising an electronic record into another, generally smaller, set of bits (the message digest) without requiring the use of any secret information such as a key, such that an electronic record yields the same message digest every time the algorithm is executed using such record as input and it is computationally unfeasible that any 2 electronic records can be found or deliberately generated that would produce the same message digest using the algorithm unless the 2 records are precisely identical.
    "Operational period of a certificate" begins on the date and time the certificate is issued by a certification authority (or on a later date and time certain if stated in the certificate) and ends on the date and time it expires as noted in the certificate or is earlier revoked, but does not include any period during which a certificate is suspended.
    "Person" means an individual, corporation, business trust, estate, trust, partnership, limited partnership, limited liability partnership, limited liability company, association, joint venture, government, governmental subdivision, agency, or instrumentality, or any other legal or commercial entity.
    "Private key" means the key of a key pair used to create a digital signature.
    "Public key" means the key of a key pair used to verify a digital signature.
    "Record" means information that is inscribed, stored, or otherwise fixed on a tangible medium or that is stored in an electronic or other medium and is retrievable in perceivable form.
    "Repository" means a system for storing and retrieving certificates or other information relevant to certificates, including information relating to the status of a certificate.
    "Revoke a certificate" means to permanently end the operational period of a certificate from a specified time forward.
    "Rule of law" means any statute, ordinance, common law rule, court decision, or other rule of law enacted, established or promulgated by the State of Illinois, or any agency, commission, department, court, other authority or political subdivision of the State of Illinois.
    "Security procedure" means a methodology or procedure used for the purpose of (1) verifying that an electronic record is that of a specific person or (2) detecting error or alteration in the communication, content, or storage of an electronic record since a specific point in time. A security procedure may require the use of algorithms or codes, identifying words or numbers, encryption, answer back or acknowledgment procedures, or similar security devices.
    "Signature device" means unique information, such as codes, algorithms, letters, numbers, private keys, or personal identification numbers (PINs), or a uniquely configured physical device, that is required, alone or in conjunction with other information or devices, in order to create an electronic signature attributable to a specific person.
    "Signed" or "signature" includes any symbol executed or adopted, or any security procedure employed or adopted, using electronic means or otherwise, by or on behalf of a person with intent to authenticate a record.
    "State agency" means and includes all officers, boards, commissions, courts, and agencies created by the Illinois Constitution, whether in the executive, legislative or judicial branch, all officers, departments, boards, commissions, agencies, institutions, authorities, universities, bodies politic and corporate of the State; and administrative units or corporate outgrowths of the State government which are created by or pursuant to statute, other than units of local government and their officers, school districts and boards of election commissioners; all administrative units and corporate outgrowths of the above and as may be created by executive order of the Governor.
    "Subscriber" means a person who is the subject named or otherwise identified in a certificate, who controls a private key that corresponds to the public key listed in that certificate, and who is the person to whom digitally signed messages verified by reference to such certificate are to be attributed.
    "Suspend a certificate" means to temporarily suspend the operational period of a certificate for a specified time period or from a specified time forward.
    "Trustworthy manner" means through the use of computer hardware, software, and procedures that, in the context in which they are used: (a) can be shown to be reasonably resistant to penetration, compromise, and misuse; (b) provide a reasonable level of reliability and correct operation; (c) are reasonably suited to performing their intended functions or serving their intended purposes; (d) comply with applicable agreements between the parties, if any; and (e) adhere to generally accepted security procedures.
    "Valid certificate" means a certificate that a certification authority has issued and that the subscriber listed in the certificate has accepted.
    "Verify a digital signature" means to use the public key listed in a valid certificate, along with the appropriate message digest function and asymmetric cryptosystem, to evaluate a digitally signed electronic record, such that the result of the process concludes that the digital signature was created using the private key corresponding to the public key listed in the certificate and the electronic record has not been altered since its digital signature was created.
(Source: P.A. 90-759, eff. 7-1-99.)