Techniques for user authentication

A computer-implemented method for user authentication, comprising:

• under control of one or more computer systems configured with executable instructions,
• receiving, from a client device, an authentication request to access a network resource on behalf of a user, the request including a user identifier for the user;
• obtaining, based on the user identifier in the received authentication request, a security phrase previously specified by the user that includes a plurality of characters;
• generating an authorization code based on the obtained security phrase, the generating including selecting a first subset of the characters in the security phrase to use for the authorization code and excluding a distinct second subset of the characters in the security phrase from use for the authorization code;
• providing, to the client device, instructions to obtain first information from the user corresponding to the generated authorization code;
• receiving, from the client device, the first information provided by the user in response to the provided instructions, the first information not including the second subset of characters;
• and
• if the first information matches the generated authorization code, authorizing the access to the network resource, and otherwise not authorizing the access to the network resource.

A computer system comprising:

• at least one processor;
• and
• at least one memory having computer-executable instructions that, when executed on the at least one processor, cause the at least one processor to:
• receive, from a client device, an authentication request to access a network resource on behalf of a user, the request including a user identifier for the user;
• obtain, based on the user identifier in the received authentication request, security information previously specified by the user;
• generate an authorization code based on the obtained security information, the generating including using a first subset of the security information for the authorization code and excluding a distinct second subset of the security information from use for the authorization code;
• provide, to the client device, instructions to obtain first information from the user corresponding to the generated authorization code;
• receive, from the client device, the first information provided by the user in response to the provided instructions, the first information not including the second subset of the security information;
• and
• if the first information corresponds to the generated authorization code, authorize the access to the network resource.

A non-transitory computer-readable medium having computer-executable instructions stored thereon that, when executed by a computer, cause the computer to:

• receive, from a client device, an authentication request to access a network resource on behalf of a user, the request including a user identifier for the user;
• obtain, based on the user identifier in the received authentication request, a previously specified security phrase having a plurality of characters;
• generate an authorization code based on the obtained security phrase, the generating including using a first subset of the characters in the security phrase for the authorization code;
• provide, to the client device, instructions to obtain first information corresponding to the generated authorization code;
• receive, from the client device, the first information provided in response to the provided instructions, the first information not including a second subset of the characters that is distinct from the first subset;
• and
• if the first information corresponds to the generated authorization code, authorize the access to the network resource.