Ciencias Informáticas criptografía Cryptography Estudo Comparativo Internet sistema operativo Algorithms Architectures Commercial services Comparative Study Comparative study Computer security Criptografia Criptografia de Chave Pública Criptografia, Cryptographic controls Cryptography protocols Digital money Dinheiro Digital Electronic Commerce Estudo comparativo Information Systems Informática Matemática Protocolos Criptográficos Public key cryptography Public key cryptosystems SOFTWARE ENGINEERING Security and Protection Segurança computacional