Add Public_Key::estimated_strength which gives an approximation of how

hard that key is to break.

Use it in cert path validation, rejecting keys with estimated strength
less than 80 bits.

2 files changed, 8 insertions, 0 deletions

diff --git a/src/pubkey/ecc_key/ecc_key.cpp b/src/pubkey/ecc_key/ecc_key.cpp
index 367b27584..22bc41249 100644
--- a/src/pubkey/ecc_key/ecc_key.cpp
+++ b/src/pubkey/ecc_key/ecc_key.cpp
@@ -18,6 +18,11 @@
 
 namespace Botan {
 
+size_t EC_PublicKey::estimated_strength() const
+   {
+   return domain().get_curve().get_p().bits() / 2;
+   }
+
 EC_PublicKey::EC_PublicKey(const EC_Group& dom_par,
                            const PointGFp& pub_point) :
    domain_params(dom_par), public_key(pub_point),
diff --git a/src/pubkey/ecc_key/ecc_key.h b/src/pubkey/ecc_key/ecc_key.h
index 76a63a7e4..de980608a 100644
--- a/src/pubkey/ecc_key/ecc_key.h
+++ b/src/pubkey/ecc_key/ecc_key.h
@@ -78,6 +78,9 @@ class BOTAN_DLL EC_PublicKey : public virtual Public_Key
       */
       EC_Group_Encoding domain_format() const
          { return domain_encoding; }
+
+      size_t estimated_strength() const override;
+
    protected:
       EC_PublicKey() : domain_encoding(EC_DOMPAR_ENC_EXPLICIT) {}