diff options
Diffstat (limited to 'node/EllipticCurveKeyPair.cpp')
| -rw-r--r-- | node/EllipticCurveKeyPair.cpp | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/node/EllipticCurveKeyPair.cpp b/node/EllipticCurveKeyPair.cpp index bed0725e..66acf320 100644 --- a/node/EllipticCurveKeyPair.cpp +++ b/node/EllipticCurveKeyPair.cpp @@ -55,7 +55,20 @@ public: }; static _EC_Group ZT_EC_GROUP; -/* Key derivation function */ +/** + * Key derivation function + * + * TODO: + * If/when we document the protocol, this will have to be documented as + * well. It's a fairly standard KDF that uses SHA-256 to transform the + * raw EC key. It's generally considered good crypto practice to do this + * to eliminate the possibility of leaking information from EC exchange to + * downstream algorithms. + * + * In our code it is used to produce a two 32-bit keys. One key is used + * for Salsa20 and the other for HMAC-SHA-256. They are generated together + * as a single 64-bit key. + */ static void *_zt_EC_KDF(const void *in,size_t inlen,void *out,size_t *outlen) { SHA256_CTX sha; @@ -130,9 +143,8 @@ bool EllipticCurveKeyPair::generate() fread(tmp,sizeof(tmp),1,rf); fclose(rf); } else { - fprintf(stderr,"WARNING: cannot open /dev/urandom\n"); - for(unsigned int i=0;i<sizeof(tmp);++i) - tmp[i] = (unsigned char)(rand() >> 3); + fprintf(stderr,"FATAL: could not open /dev/urandom\n"); + exit(-1); } RAND_seed(tmp,sizeof(tmp)); #else |