In the pre-Web era, computers were large and expensive, and were usually shared by multiple users. As a result, methods to keep users and their data protected from one another within such systems were important, and Government contracts supported extensive research and development in this area. The Multics time-sharing system was an important example, and served as a precursor to the smaller Unix and Linux systems that are widely used to this day. The US National Security Agency (NSA)'s National Computer Security Center (NCSC) created the Trusted Computer System Evaluation Criteria (TCSEC, more commonly known as the "Orange Book"), which specified system requirements ranging up to levels intended for use with classified military data.

The Data Encryption Standard was developed during the 1970s and standardized by the U.S. National Bureau of Standards in 1977 as Federal Information Processing Standard (FIPS) 46, and provided the first widely-used method for computer-based encryption. It was a symmetric algorithm, encrypting and decrypting 64-bit data blocks with 56-bit keys, performing steps including those shown in the attached diagram. Given the speed of computers at the time, special hardware was often needed to run DES with sufficient performance.

With public-key cryptography, keys are used in pairs, where one member of a pair (the public key) is used to encrypt messages or check their signatures, and the other member (the private key) is used to decrypt or sign messages. In most usage, public keys can be circulated freely, while private keys are carefully protected. Public-key algorithms are usually applied in combination with symmetric algorithms, helping to manage trust between parties in an effective manner. In 1977, MIT professors Rivest, Shamir, and Adleman published RSA, the first practical public-key encryption algorithm.

The Kerberos authentication system, developed in the late 1980s at MIT's Project Athena, authenticates users to services using symmetric cryptography and an authentication server. Kerberos technology is still used today, particularly in Microsoft domains.

Email was a primary application of early interest within and beyond the Internet, and motivated early interest in security. The Privacy-Enhanced Mail (PEM) project, initiated in the 1980s, prototyped methods for email encryption and provided a pilot example for use of public-key certificates and an associated Public-Key Infrastructure (PKI) in the Internet context. It provided a proof of concept for the subsequent Secure/Multipurpose Internet Mail Extensions (S/MIME) messaging security protocols, which have been widely implemented in email clients though have been less widely used.