Use strict data encryption with a proven encryption technique
Use protocol algorithms that are currently considered to be strong by experts in the field, and select well-tested implementations.
For countering spoofing and session hijacking:
Use Transport Layer Security (TLS), Secure Shell (SSH), HTTP Secure (HTTPS) and other secure communications protocols that encrypt data before it is sent and authenticate data as it is received.
Use additional multistep authentication methods.
Weaknesses in password hashing algorithms can be used to steal sensitive information stored on a web or application server. Use cryptographic hash functions to implement password hashing.
Use pentesting. Even the best senior programmers are susceptible to making mistakes. Review the application for potential vulnerabilities. For best results, do it regularly.