This information relates to the current Canvas Classic Quiz tool, not New Quizzes, which is currently available but not yet standard Canvas functionality.
Introduction
There are several ways in Canvas to show students the answers to a Canvas Quiz, but they all have implications for quiz security or instructor workload. In all of these cases, because the key is out there, the quiz can be shared with future semesters' students. You will find more information on Canvas Quiz settings to maximize Security, but this article focuses on understanding your options for showing answers.
Option 1 - Easy workload, security problems
Set up the dates so no one can take the quiz after a certain date. Check "Let Students See Their Quiz Responses (Incorrect Questions Will Be Marked in Student Feedback)" and "Let Students See The Correct Answers" adding the due date as the date to show correct answers. However, after students take the quiz they will be able to see all their questions and all their answers, and the answers will be marked correct and incorrect (correct answers for incorrect questions will not show until after the quiz is no longer available). So the correct answers can get out before the quiz is done. Students that do not take the quiz will never see the questions or correct answers.
Option 2 - Easy workload, security problems
Set up the quiz so that students can see their answers and the correct answers only once, immediately after the quiz by checking "Let Students See Their Quiz Responses (Incorrect Questions Will Be Marked in Student Feedback)" and "Only Once After Each Attempt". Once studnets leave the page, they do not get to see their answers again, but again answers can get out before the quiz is closed. If you are having students take the quiz online in a proctored room, this might be a good option. Students that do not take the quiz will never see the questions or correct answers.
Option 3 - Increase workload, quiz secure during semester
Set the quiz so students cannot see their quiz responses by unchecking "Let Students See Their Quiz Responses (Incorrect Questions Will Be Marked in Student Feedback)" and set an Until date that prevents students from taking the quiz after a certain date. Students will be able to see their scores but not their correct and incorrect answers. After the Until date or when all exams are taken, the instructor can go into settings and check the box to "Let Students See Their Quiz Responses (Incorrect Questions Will Be Marked in Student Feedback)", and "Let Students See The Correct Answers" and choose dates. With this setup, correct answers can not get out during the quiz, but might be passed to future students. Students that do not take the quiz will never see the questions or correct answers. When starting up a new semester, and instructor would need to uncheck that box for all the quizzes. (Settings before on the top, after on the bottom.)
Option 4 - Increase workload, quiz secure during semester
Create a document with the key and have it in modules unpublished. After the quiz Until date, publish it. When starting up a new semester, and instructor would need to unpublish the keys for all the quizzes.
For ultimate security for quizzes, the best option is to never let students see the quiz responses after taking a quiz and never see the key or answers.