Issuance and authentication of digital signatures in electronic transactions or communications over the Internet or other computer network; issuance and management of digital certificates for authentication of digital communications; protecting the security of data transmitted over computer networks by means of authentication of use identity and message content, verification of non-repudiation of transmissions and access control; issuing and managing digital certificates for authenticating and validating digital content in connection with communications related to commercial transactions, online bidding activity, and medical records; confirming for others the non-repudiation of digital communications related to commercial transactions, online bidding activity, and medical records; providing confirmation to others of the time of acceptance of digital communications; protecting the security of data transmitted over computer networks by means of authentication of user identity and message content; verifying for others the non-repudiation of digital transmissions over the Internet or an Intranet; authentication and validation services in the field of digital content transmitted over the Internet or an Intranet; computer security services, namely, providing message encryption and decryption, firewall protection, authentication, control and certification of electronic messages by introducing and checking electronic signatures; development, design, implementation, testing, analysis, and consulting services in the field of security, access, authorization, authentication encryption, and identification systems for computers, computer hardware and computer networks; digital communication security services for public key infrastructures; development, design, integration and operation of computer systems to support issuance and management of digital signatures and certificates