암호학 참조 문헌
독일 교수 암호학 강의 문서: Understanding cryptography
강의 동영상: Introduction to Cryptography
암호학 자료: Crypto-Hashing and applications
256bit 해시함수의 충돌 찾기: https://crypto.stackexchange.com/questions/39641/what-are-the-odds-of-collisions-for-a-hash-function-with-256-bit-output
SHA-256: http://www.iwar.org.uk/comsec/resources/cipher/sha256-384-512.pdf
Layman’s guide to ECDSA: http://royalforkblog.github.io/2014/09/04/ecc/
