It is also used in eliptic and hyperelliptic curve cryptography, when you study the Jacobian Variety a curve: http://modular.math.washington.edu/edu/Fall2003/25

It is also used in eliptic and hyperelliptic curve cryptography, when you study the Jacobian Variety a curve: http://modular.math.washington.edu/edu/Fall2003/252/lectures/10-15-03/10-15-03-lecture.pdf http://modular.math.washington.edu/edu/Fall2003/252/lectures... Categories and Functors come out naturally when studying such structures.