### Question 105. What is Blakley's Secret Sharing Scheme?

Blakley's secret sharing scheme [Bla79] is geometric in nature. The secret is a point in an m-dimensional space. n shares are constructed with each share defining a hyperplane in this space. By finding the intersection of any m of these planes, the secret (or point of intersection) can be obtained. This scheme is not perfect, as the person with a share of the secret knows that the secret is a point on his hyperplane. Nevertheless, this scheme can be modified to achieve perfect security [Sim92].

Figure 10. Blakley's scheme

A special case of Blakley's scheme is shown in Figure 10. This is based on the scenario where two shares are required to recover the secret. A two-dimensional plane is used as only two shares are required to recover the secret. The secret is a point in the plane. Each share is a line that passes through the point. If any two of the shares are put together, the point of intersection, which is the secret, can be easily derived.