It is easier to provide the list of things that are worth worrying about than it is to list the things that are safe. There are a lot of as-yet unbroken ciphers and constructions. So, here are the things to avoid:
* Block ciphers in the default mode (“ECB”).
* The Dual_EC random number generator, which virtually nobody uses anyways. You weren’t going to accidentally end up using it. Or, for that matter, any other PKRNG (random numbers produced by public key algorithms).
* RSA with 1024 bit moduli (or below); RSA-2048 is your starting point. Conventional DH at similar key sizes will be an issue too, but there’s a “means/motive/opportunity” issue for RSA-1024 given its prevalence.
* MD4, MD5, and SHA1 aren’t backdoored, but are broken or weak. But: all three are survivable in HMAC (don’t use them, though). SHA2 is your best all-around hashing bet right now.
* The NIST P- curves. There’s no evidence to suggest they’re backdoored, but (a) the rationale behind their generation is questionable and (b) they have other annoying properties.
So far as I can tell, you are now fully briefed on the “distrusted” crypto.
Don’t build your own crypto. Use PGP for data at rest, TLS for data in motion, and NaCl for the rare in-between cases.
Source @tptacek: https://news.ycombinator.com/user?id=tptacek