Mathematical cryptography: Cryptography, Theory and Practice D. Stinson; An Introduction to Mathematical Cryptography, J. Hoffstein, J. Pipher and J. Silverman; A Course in Number Theory and Cryptography, N. Koblitz; Algebraic Aspects of Cryptography, N. Koblitz.
Coding: A First Course in Coding Theory R. Hill; Elements of Algebraic Coding Theory, L. Vermani; Introduction to Coding THeory, J. H. van Lint
Number Theory: A Friendly Introduction to Number Theory J. Silverman; The Theory of Numbers, G. H. Hardy and E. M. Wright.
Algebra: A First Course in Abstract Algebra, J. Fraleigh; Abstract Algebra D. S. Dummit and R. M. Foote; Topics in Algebra, I. Herstein; Basic Algebra, I., II., N. Jacobson.
Reading about Bitcoin: A particularly nice account of Bitcoin can be found by Michael Nielson.
Sage - Free, sophisticated math software for indepth exploration.
The Undergraduate Mathematics Resource Center is in Math 175 (first floor of math building), and is open M-Th 9-5 and F 9-2. Although tutors no longer serve this course, an area has been set up where you can meet your peers to work together.