Activity 17 Sharing secrets—Information hiding protocols Summary Cryptographic techniques enable us to share information with other people, yet still maintain a surprisingly high level of privacy. This activity illustrates a situation where information is shared, and yet none of it is revealed: a group of students will calculate their average age without anyone having to reveal to anyone else what their age is. Curriculum Links Mathematics Sums and averages – Skills Calculating an average Random numbers Cooperative tasks Ages 7 years and up Materials Each of students will need: a pad of paper, and a pen. Sharing Secrets Introduction This activity involves finding the average age of a group of students, without anyone having to reveal what their age is. Alternatively, one could work out the average income (allowance) of the students in the group, or some similar personal detail. Calculating these statistics works particularly well with adults, because older people can be more sensitive about details like age and income. You will need at least three students in the group. Discussion Explain to the group that you would like to work out their average age, without anyone telling anyone else what their age is. Ask for suggestions about how this might be done, or even whether they believe it can be done. Select about six to ten students to work with. Give the pad and pen to the first student, and ask them to secretly write down a randomly chosen three-digit number on the top sheet of paper. In this example, 613 has been chosen as the random number. Have the first student tear off the first page, add their age to the random number, and write it on the second sheet on the pad. The first student's age is 8, so the
Activity 17 Sharing secrets—Information hiding protocols Summary Cryptographic techniques enable us to share information with other people, yet still maintain a surprisingly high level of privacy. This activity illustrates a situation where information is shared, and yet none of it is revealed: a group of students will calculate their average age without anyone having to reveal to anyone else what their age is. Curriculum Links Mathematics – Sums and averages Skills Calculating an average Random numbers Cooperative tasks Ages 7 years and up Materials Each of students will need: a pad of paper, and a pen. Sharing Secrets Introduction This activity involves finding the average age of a group of students, without anyone having to reveal what their age is. Alternatively, one could work out the average income (allowance) of the students in the group, or some similar personal detail. Calculating these statistics works particularly well with adults, because older people can be more sensitive about details like age and income. You will need at least three students in the group. Discussion Explain to the group that you would like to work out their average age, without anyone telling anyone else what their age is. Ask for suggestions about how this might be done, or even whether they believe it can be done. Select about six to ten students to work with. Give the pad and pen to the first student, and ask them to secretly write down a randomly chosen three-digit number on the top sheet of paper. In this example, 613 has been chosen as the random number. Have the first student tear off the first page, add their age to the random number, and write it on the second sheet on the pad. The first student's age is 8, so the
CSUnplugged_OS_2015_v3.1.docx