Extract special case for six characters and rework bruteforce recovery

include/password.hpp

@@ -4,73 +4,8 @@
 #include "Keys.hpp"
 #include "Progress.hpp"
 
-#include <bitset>
-#include <mutex>
-
 /// \file password.hpp
 
-/// Class to recover a password from internal keys
-class Recovery
-{
-public:
-    /// Constructor
-    Recovery(const Keys& keys, const std::vector<std::uint8_t>& charset, std::vector<std::string>& solutions,
-             std::mutex& solutionsMutex, bool exhaustive, Progress& progress);
-
-    /// \brief Look for a password of length 6 or less
-    ///
-    /// Try to derive 6 characters such that updating the given cipher state
-    /// with them gives the target cipher state (the password representation).
-    /// On success, the current prefix followed by those 6 characters is added
-    /// to the shared output vector.
-    ///
-    /// If the target length is less than 6, the first characters are ignored so that
-    /// the saved solution has the target length. This is useful to recover passwords
-    /// shorter than 6 characters.
-    ///
-    /// \pre prefix.size() + 6 == length && initial == Keys{prefix} || length < 6
-    void recoverShortPassword(const Keys& initial);
-
-    /// \brief Look for password of length 7 or more
-    ///
-    /// Recursively iterate on possible prefixes of length-6 characters.
-    /// For each prefix, try to recover the last 6 characters like recoverShortPassword.
-    ///
-    /// \pre prefix.size() + 6 < length && initial == Keys{prefix}
-    void recoverLongPassword(const Keys& initial);
-
-    /// Length of the password to recover
-    std::size_t length;
-
-    /// The first characters of the password candidate, up to length-6 characters long
-    std::string prefix;
-
-    /// Set of characters to generate password candidates
-    const std::vector<std::uint8_t>& charset;
-
-private:
-    // iterate recursively on possible Y values
-    void recursion(int i);
-
-    // set of possible Z0[16,31) values considering given character set
-    std::bitset<1 << 16> z0_16_32;
-
-    // set of possible Z{-1}[24,32) values considering given character set
-    std::bitset<1 << 8> zm1_24_32;
-
-    // cipher state (X,Y,Z)_i for index i in [0, 6] where the last state (X,Y,Z)_6 is
-    // the representation of the password to recover
-    std::array<std::uint32_t, 7> x, y, z;
-    std::uint32_t                candidateX0; // backup of candidate X value for convenience
-
-    std::array<std::uint8_t, 6> p; // password last 6 bytes
-
-    std::vector<std::string>& solutions; // shared output vector of valid passwords
-    std::mutex&               solutionsMutex;
-    const bool                exhaustive;
-    Progress&                 progress;
-};
-
 /// \brief Try to recover the password associated with the given keys
 /// \param keys Internal keys for which a password is wanted
 /// \param charset The set of characters with which to constitute password candidates