/* * Determine whether two keystructs have compatible parameters (i.e., same * twist and curveParams). Return 0 if compatible, else non-zero. */ static int keys_inconsistent(key pub1, key pub2){ if(!curveParamsEquivalent(pub1->cp, pub2->cp)) { return CURVE_PARAM_MISMATCH; } if(pub1->twist != pub2->twist) { return TWIST_PARAM_MISMATCH; } return 0; }
/* * Alloc and init a feeFEED object associated with specified public and * private keys. */ feeFEED feeFEEDNewWithPubKey(feePubKey myPrivKey, feePubKey theirPubKey, int forEncrypt, // 0 ==> decrypt 1 ==> encrypt feeRandFcn randFcn, // optional void *randRef) { feedInst *finst; giant privGiant; key k; unsigned expPlainSize; unsigned expCipherSize; unsigned expBlocks; if(!curveParamsEquivalent(feePubKeyCurveParams(theirPubKey), feePubKeyCurveParams(myPrivKey))) { dbgLog(("feeFEEDNewWithPubKey: Incompatible Keys\n")); return NULL; } finst = (feedInst*) fmalloc(sizeof(feedInst)); bzero(finst, sizeof(feedInst)); finst->forEncrypt = forEncrypt; finst->cp = curveParamsCopy(feePubKeyCurveParams(theirPubKey)); finst->rsBlockCount = 0; finst->xp = newGiant(finst->cp->maxDigits); finst->xm = newGiant(finst->cp->maxDigits); finst->tmp1 = newGiant(finst->cp->maxDigits); if(forEncrypt) { finst->tmp2 = newGiant(finst->cp->maxDigits); } /* * cluePlus = ourPriv * theirPub+ * clueMinus = ourPriv * theirPub- */ finst->cluePlus = newGiant(finst->cp->maxDigits); finst->clueMinus = newGiant(finst->cp->maxDigits); privGiant = feePubKeyPrivData(myPrivKey); if(privGiant == NULL) { dbgLog(("feeFEEDNewWithPubKey: no private key\n")); goto abort; } k = feePubKeyPlusCurve(theirPubKey); gtog(k->x, finst->cluePlus); // cluePlus = theirPub+ elliptic_simple(finst->cluePlus, privGiant, finst->cp); k = feePubKeyMinusCurve(theirPubKey); gtog(k->x, finst->clueMinus); // theirPub- elliptic_simple(finst->clueMinus, privGiant, finst->cp); /* * Set up block sizes. */ if(finst->cp->primeType == FPT_General) { unsigned blen = bitlen(finst->cp->basePrime); finst->plainBlockSize = blen / 8; if((blen & 0x7) == 0) { /* * round down some more... */ finst->plainBlockSize--; } } else { finst->plainBlockSize = finst->cp->q / 8; if(((finst->cp->q & 0x7) == 0) && (finst->cp->k > 0)) { /* * Special case, with q mod 8 == 0. Here we have to * trim back the plainBlockSize by one byte. */ finst->plainBlockSize--; } } finst->cipherBlockSize = finst->cp->minBytes + 1; /* * the size of initialRS is subject to tweaking - if we make it * not a multiple of plainBlockSize, we save one FEEDExp cipherBlock * in our ciphertext. */ finst->initialRSSize = finst->plainBlockSize * 2; if(finst->initialRSSize > RS_MIN_SIZE) { unsigned minPlainBlocks; unsigned maxSize; /* * How many plainblocks to hold RS_MIN_SIZE? */ minPlainBlocks = (RS_MIN_SIZE + finst->plainBlockSize - 1) / finst->plainBlockSize; /* * Max size = that many plainblocks, less 2 bytes (to avoid * extra residue block). */ maxSize = minPlainBlocks * finst->plainBlockSize - 2; /* * But don't bother with more than 2 plainblocks worth */ if(finst->initialRSSize > maxSize) { finst->initialRSSize = maxSize; } } /* else leave it alone, that's small enough */ if(forEncrypt) { feeRand frand = NULL; /* * Encrypt-capable FEEDExp object */ finst->feedExp = feeFEEDExpNewWithPubKey(theirPubKey, randFcn, randRef); if(finst->feedExp == NULL) { goto abort; } /* * Generate initial r and s data. */ finst->initialRS = (unsigned char*) fmalloc(finst->initialRSSize); if(randFcn != NULL) { randFcn(randRef, finst->initialRS, finst->initialRSSize); } else { frand = feeRandAlloc(); feeRandBytes(frand, finst->initialRS, finst->initialRSSize); feeRandFree(frand); } if(initFromRS(finst)) { goto abort; } } else { /* * Decrypt-capable FEEDExp object */ finst->feedExp = feeFEEDExpNewWithPubKey(myPrivKey, randFcn, randRef); if(finst->feedExp == NULL) { goto abort; } } /* * Figure out how many of our cipherblocks it takes to hold * a FEEDExp-encrypted initialRS. If initialRSSize is an exact * multiple of expPlainSize, we get an additional feedExp * residue block. */ expPlainSize = feeFEEDExpPlainBlockSize(finst->feedExp); expCipherSize = feeFEEDExpCipherBlockSize(finst->feedExp); expBlocks = (finst->initialRSSize + expPlainSize - 1) / expPlainSize; if((finst->initialRSSize % expPlainSize) == 0) { expBlocks++; } /* * Total meaningful bytes of encrypted initialRS */ finst->rsCtextSize = expBlocks * expCipherSize; /* * Number of our cipherblocks it takes to hold rsCtextSize */ finst->rsSizeCipherBlocks = (finst->rsCtextSize + finst->cipherBlockSize - 1) / finst->cipherBlockSize; if(!forEncrypt) { finst->rsCtext = (unsigned char*) fmalloc(finst->rsSizeCipherBlocks * finst->cipherBlockSize); } /* * Sanity check... */ #if FEED_DEBUG { unsigned fexpBlockSize = feeFEEDExpCipherBlockSize(finst->feedExp); /* * FEEDExp has one more giant in ciphertext, plaintext is * same size */ if((finst->cipherBlockSize + finst->cp->minBytes) != fexpBlockSize) { dbgLog(("feeFEEDNewWithPubKey: FEEDExp CBlock Size " "screwup\n")); goto abort; } fexpBlockSize = feeFEEDExpPlainBlockSize(finst->feedExp); if(fexpBlockSize != finst->plainBlockSize) { dbgLog(("feeFEEDNewWithPubKey: FEEDExp PBlock Size " "screwup\n")); goto abort; } } #endif // FEED_DEBUG return finst; abort: feeFEEDFree(finst); return NULL; }