What is the best C crypto library for small devices? My device is very limited in memory (only about 50 KB left). Also I do not need all of the fancy cryptography algorithms. An encryption, MAC algorithm and a CSPRNG is enough.

I've tried the following but they are simply too big:

  • OpenSSL
  • Cryptlib
  • NaCl
  • Nettle
  • WolfSSL
  • mbedTLS
  • If you link statically, you shouldn't care about the library size, no? – mustaccio Aug 14 '15 at 20:04


This is amazons attempt to rebuild openssl with only the modern features needed. It has according to amazon passed 3 security audits.

It has something like 6,000 lines of code.

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