diff options
| -rw-r--r-- | src/cli/pubkey.cpp | 34 | ||||
| -rw-r--r-- | src/lib/pubkey/workfactor.cpp | 31 |
2 files changed, 53 insertions, 12 deletions
diff --git a/src/cli/pubkey.cpp b/src/cli/pubkey.cpp index 5a8cfcf44..3af91b722 100644 --- a/src/cli/pubkey.cpp +++ b/src/cli/pubkey.cpp @@ -17,6 +17,7 @@ #include <botan/pk_algs.h> #include <botan/pkcs8.h> #include <botan/pubkey.h> +#include <botan/workfactor.h> #if defined(BOTAN_HAS_DL_GROUP) #include <botan/dl_group.h> @@ -392,6 +393,39 @@ class DL_Group_Info final : public Command BOTAN_REGISTER_COMMAND("dl_group_info", DL_Group_Info); +class PK_Workfactor final : public Command + { + public: + PK_Workfactor() : Command("pk_workfactor --type=rsa bits") {} + + std::string group() const override + { + return "pubkey"; + } + + std::string description() const override + { + return "Provide estimate of strength of public key based on size"; + } + + void go() override + { + const size_t bits = get_arg_sz("bits"); + const std::string type = get_arg("type"); + + if(type == "rsa") + output() << Botan::if_work_factor(bits) << "\n"; + else if(type == "dl") + output() << Botan::dl_work_factor(bits) << "\n"; + else if(type == "dl_exp") + output() << Botan::dl_exponent_size(bits) << "\n"; + else + throw CLI_Usage_Error("Unknown type for pk_workfactor"); + } + }; + +BOTAN_REGISTER_COMMAND("pk_workfactor", PK_Workfactor); + class Gen_DL_Group final : public Command { public: diff --git a/src/lib/pubkey/workfactor.cpp b/src/lib/pubkey/workfactor.cpp index 8be64bef3..71604c06b 100644 --- a/src/lib/pubkey/workfactor.cpp +++ b/src/lib/pubkey/workfactor.cpp @@ -16,21 +16,32 @@ size_t ecp_work_factor(size_t bits) return bits / 2; } -size_t if_work_factor(size_t bits) - { - // RFC 3766: k * e^((1.92 + o(1)) * cubrt(ln(n) * (ln(ln(n)))^2)) - // It estimates k at .02 and o(1) to be effectively zero for sizes of interest - const double k = .02; +namespace { - // approximates natural logarithm of p +size_t nfs_workfactor(size_t bits, double k) + { + // approximates natural logarithm of integer of given bitsize const double log2_e = std::log2(std::exp(1)); const double log_p = bits / log2_e; - const double est = 1.92 * std::pow(log_p * std::log(log_p) * std::log(log_p), 1.0/3.0); + const double log_log_p = std::log(log_p); + // RFC 3766: k * e^((1.92 + o(1)) * cubrt(ln(n) * (ln(ln(n)))^2)) + const double est = 1.92 * std::pow(log_p * log_log_p * log_log_p, 1.0/3.0); + + // return log2 of the workfactor return static_cast<size_t>(std::log2(k) + log2_e * est); } +} + +size_t if_work_factor(size_t bits) + { + // RFC 3766 estimates k at .02 and o(1) to be effectively zero for sizes of interest + + return nfs_workfactor(bits, .02); + } + size_t dl_work_factor(size_t bits) { // Lacking better estimates... @@ -46,12 +57,8 @@ size_t dl_exponent_size(size_t bits) (this only matters for very small primes). */ const size_t MIN_WORKFACTOR = 64; - const double log2_e = std::log2(std::exp(1)); - const double log_p = bits / log2_e; - - const double strength = 1.92 * std::pow(log_p, 1.0/3.0) * std::pow(std::log(log_p), 2.0/3.0); - return 2 * std::max<size_t>(MIN_WORKFACTOR, static_cast<size_t>(log2_e * strength)); + return 2 * std::max<size_t>(MIN_WORKFACTOR, nfs_workfactor(bits, 1)); } } |