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authorJack Lloyd <[email protected]>2019-08-24 09:36:37 -0400
committerJack Lloyd <[email protected]>2019-08-24 09:36:37 -0400
commitb6fc31f9086c9a4af0775974834b6f0847437721 (patch)
tree06ca98acff01dc6157dd7559a4e6ef45d21937e7 /src/lib
parentab21733fdd5024cfc98d6e77e2cb7d79be2d84e3 (diff)
parent24959678e8e202b17ddf3a964495e92c1a39f7d3 (diff)
Merge GH #2080 Remove use of pow_mod.h interfaces from within library
Diffstat (limited to 'src/lib')
-rw-r--r--src/lib/math/numbertheory/def_powm.h68
-rw-r--r--src/lib/math/numbertheory/info.txt1
-rw-r--r--src/lib/math/numbertheory/numthry.cpp42
-rw-r--r--src/lib/math/numbertheory/pow_mod.cpp136
-rw-r--r--src/lib/math/numbertheory/pow_mod.h19
-rw-r--r--src/lib/math/numbertheory/powm_fw.cpp65
-rw-r--r--src/lib/math/numbertheory/powm_mnt.cpp46
-rw-r--r--src/lib/prov/pkcs11/p11_rsa.cpp5
-rw-r--r--src/lib/pubkey/dh/dh.cpp24
-rw-r--r--src/lib/pubkey/elgamal/elgamal.cpp37
10 files changed, 202 insertions, 241 deletions
diff --git a/src/lib/math/numbertheory/def_powm.h b/src/lib/math/numbertheory/def_powm.h
deleted file mode 100644
index 6b1f33835..000000000
--- a/src/lib/math/numbertheory/def_powm.h
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
-* Modular Exponentiation
-* (C) 1999-2007 Jack Lloyd
-*
-* Botan is released under the Simplified BSD License (see license.txt)
-*/
-
-#ifndef BOTAN_DEFAULT_MODEXP_H_
-#define BOTAN_DEFAULT_MODEXP_H_
-
-#include <botan/pow_mod.h>
-#include <botan/reducer.h>
-#include <vector>
-
-namespace Botan {
-
-/**
-* Fixed Window Exponentiator
-*/
-class Fixed_Window_Exponentiator final : public Modular_Exponentiator
- {
- public:
- void set_exponent(const BigInt&) override;
- void set_base(const BigInt&) override;
- BigInt execute() const override;
-
- Modular_Exponentiator* copy() const override
- { return new Fixed_Window_Exponentiator(*this); }
-
- Fixed_Window_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
- private:
- Modular_Reducer m_reducer;
- BigInt m_exp;
- size_t m_window_bits;
- std::vector<BigInt> m_g;
- Power_Mod::Usage_Hints m_hints;
- };
-
-class Montgomery_Params;
-class Montgomery_Exponentation_State;
-
-/**
-* Montgomery Exponentiator
-*/
-class Montgomery_Exponentiator final : public Modular_Exponentiator
- {
- public:
- void set_exponent(const BigInt&) override;
- void set_base(const BigInt&) override;
- BigInt execute() const override;
-
- Modular_Exponentiator* copy() const override
- { return new Montgomery_Exponentiator(*this); }
-
- Montgomery_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
- private:
- BigInt m_p;
- Modular_Reducer m_mod_p;
- std::shared_ptr<const Montgomery_Params> m_monty_params;
- std::shared_ptr<const Montgomery_Exponentation_State> m_monty;
-
- BigInt m_e;
- Power_Mod::Usage_Hints m_hints;
- };
-
-}
-
-#endif
diff --git a/src/lib/math/numbertheory/info.txt b/src/lib/math/numbertheory/info.txt
index 0ebd1e05f..4b241c120 100644
--- a/src/lib/math/numbertheory/info.txt
+++ b/src/lib/math/numbertheory/info.txt
@@ -12,7 +12,6 @@ monty.h
<header:internal>
primality.h
-def_powm.h
monty_exp.h
</header:internal>
diff --git a/src/lib/math/numbertheory/numthry.cpp b/src/lib/math/numbertheory/numthry.cpp
index 7af1d13df..a69028189 100644
--- a/src/lib/math/numbertheory/numthry.cpp
+++ b/src/lib/math/numbertheory/numthry.cpp
@@ -1,12 +1,11 @@
/*
* Number Theory Functions
-* (C) 1999-2011,2016,2018 Jack Lloyd
+* (C) 1999-2011,2016,2018,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/numthry.h>
-#include <botan/pow_mod.h>
#include <botan/reducer.h>
#include <botan/monty.h>
#include <botan/divide.h>
@@ -427,29 +426,34 @@ BigInt power_mod(const BigInt& base, const BigInt& exp, const BigInt& mod)
return 0;
}
- Power_Mod pow_mod(mod);
+ Modular_Reducer reduce_mod(mod);
- /*
- * Calling set_base before set_exponent means we end up using a
- * minimal window. This makes sense given that here we know that any
- * precomputation is wasted.
- */
+ const size_t exp_bits = exp.bits();
- if(base.is_negative())
+ if(mod.is_odd())
{
- pow_mod.set_base(-base);
- pow_mod.set_exponent(exp);
- if(exp.is_even())
- return pow_mod.execute();
- else
- return (mod - pow_mod.execute());
+ const size_t powm_window = 4;
+
+ auto monty_mod = std::make_shared<Montgomery_Params>(mod, reduce_mod);
+ auto powm_base_mod = monty_precompute(monty_mod, reduce_mod.reduce(base), powm_window);
+ return monty_execute(*powm_base_mod, exp, exp_bits);
}
- else
+
+ /*
+ Support for even modulus is just a convenience and not considered
+ cryptographically important, so this implementation is slow ...
+ */
+ BigInt accum = 1;
+ BigInt g = reduce_mod.reduce(base);
+ BigInt t;
+
+ for(size_t i = 0; i != exp_bits; ++i)
{
- pow_mod.set_base(base);
- pow_mod.set_exponent(exp);
- return pow_mod.execute();
+ t = reduce_mod.multiply(g, accum);
+ g = reduce_mod.square(g);
+ accum.ct_cond_assign(exp.get_bit(i), t);
}
+ return accum;
}
diff --git a/src/lib/math/numbertheory/pow_mod.cpp b/src/lib/math/numbertheory/pow_mod.cpp
index 02434fe68..7b38fad1d 100644
--- a/src/lib/math/numbertheory/pow_mod.cpp
+++ b/src/lib/math/numbertheory/pow_mod.cpp
@@ -1,15 +1,145 @@
/*
* Modular Exponentiation Proxy
-* (C) 1999-2007 Jack Lloyd
+* (C) 1999-2007,2012,2018,2019 Jack Lloyd
+* 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/pow_mod.h>
-#include <botan/internal/def_powm.h>
+#include <botan/numthry.h>
+#include <botan/reducer.h>
+#include <botan/monty.h>
+#include <botan/internal/monty_exp.h>
+#include <botan/internal/rounding.h>
+#include <vector>
namespace Botan {
+class Modular_Exponentiator
+ {
+ public:
+ virtual void set_base(const BigInt&) = 0;
+ virtual void set_exponent(const BigInt&) = 0;
+ virtual BigInt execute() const = 0;
+ virtual Modular_Exponentiator* copy() const = 0;
+
+ Modular_Exponentiator() = default;
+ Modular_Exponentiator(const Modular_Exponentiator&) = default;
+ Modular_Exponentiator & operator=(const Modular_Exponentiator&) = default;
+ virtual ~Modular_Exponentiator() = default;
+ };
+
+namespace {
+
+/**
+* Fixed Window Exponentiator
+*/
+class Fixed_Window_Exponentiator final : public Modular_Exponentiator
+ {
+ public:
+ void set_exponent(const BigInt& e) override { m_exp = e; }
+ void set_base(const BigInt&) override;
+ BigInt execute() const override;
+
+ Modular_Exponentiator* copy() const override
+ { return new Fixed_Window_Exponentiator(*this); }
+
+ Fixed_Window_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
+ private:
+ Modular_Reducer m_reducer;
+ BigInt m_exp;
+ size_t m_window_bits;
+ std::vector<BigInt> m_g;
+ Power_Mod::Usage_Hints m_hints;
+ };
+
+void Fixed_Window_Exponentiator::set_base(const BigInt& base)
+ {
+ m_window_bits = Power_Mod::window_bits(m_exp.bits(), base.bits(), m_hints);
+
+ m_g.resize(static_cast<size_t>(1) << m_window_bits);
+ m_g[0] = 1;
+ m_g[1] = m_reducer.reduce(base);
+
+ for(size_t i = 2; i != m_g.size(); ++i)
+ m_g[i] = m_reducer.multiply(m_g[i-1], m_g[1]);
+ }
+
+BigInt Fixed_Window_Exponentiator::execute() const
+ {
+ const size_t exp_nibbles = (m_exp.bits() + m_window_bits - 1) / m_window_bits;
+
+ BigInt x = 1;
+
+ for(size_t i = exp_nibbles; i > 0; --i)
+ {
+ for(size_t j = 0; j != m_window_bits; ++j)
+ x = m_reducer.square(x);
+
+ const uint32_t nibble = m_exp.get_substring(m_window_bits*(i-1), m_window_bits);
+
+ // not const time:
+ x = m_reducer.multiply(x, m_g[nibble]);
+ }
+ return x;
+ }
+
+/*
+* Fixed_Window_Exponentiator Constructor
+*/
+Fixed_Window_Exponentiator::Fixed_Window_Exponentiator(const BigInt& n,
+ Power_Mod::Usage_Hints hints)
+ : m_reducer{Modular_Reducer(n)}, m_exp{}, m_window_bits{}, m_g{}, m_hints{hints}
+ {}
+
+class Montgomery_Exponentiator final : public Modular_Exponentiator
+ {
+ public:
+ void set_exponent(const BigInt& e) override { m_e = e; }
+ void set_base(const BigInt&) override;
+ BigInt execute() const override;
+
+ Modular_Exponentiator* copy() const override
+ { return new Montgomery_Exponentiator(*this); }
+
+ Montgomery_Exponentiator(const BigInt&, Power_Mod::Usage_Hints);
+ private:
+ BigInt m_p;
+ Modular_Reducer m_mod_p;
+ std::shared_ptr<const Montgomery_Params> m_monty_params;
+ std::shared_ptr<const Montgomery_Exponentation_State> m_monty;
+
+ BigInt m_e;
+ Power_Mod::Usage_Hints m_hints;
+ };
+
+void Montgomery_Exponentiator::set_base(const BigInt& base)
+ {
+ size_t window_bits = Power_Mod::window_bits(m_e.bits(), base.bits(), m_hints);
+ m_monty = monty_precompute(m_monty_params, m_mod_p.reduce(base), window_bits);
+ }
+
+BigInt Montgomery_Exponentiator::execute() const
+ {
+ /*
+ This leaks size of e via loop iterations, not possible to fix without
+ breaking this API. Round up to avoid leaking fine details.
+ */
+ return monty_execute(*m_monty, m_e, round_up(m_e.bits(), 8));
+ }
+
+Montgomery_Exponentiator::Montgomery_Exponentiator(const BigInt& mod,
+ Power_Mod::Usage_Hints hints) :
+ m_p(mod),
+ m_mod_p(mod),
+ m_monty_params(std::make_shared<Montgomery_Params>(m_p, m_mod_p)),
+ m_hints(hints)
+ {
+ }
+
+}
+
/*
* Power_Mod Constructor
*/
@@ -18,6 +148,8 @@ Power_Mod::Power_Mod(const BigInt& n, Usage_Hints hints, bool disable_monty)
set_modulus(n, hints, disable_monty);
}
+Power_Mod::~Power_Mod() { /* for ~unique_ptr */ }
+
/*
* Power_Mod Copy Constructor
*/
diff --git a/src/lib/math/numbertheory/pow_mod.h b/src/lib/math/numbertheory/pow_mod.h
index 077f4ccf7..d179d8c85 100644
--- a/src/lib/math/numbertheory/pow_mod.h
+++ b/src/lib/math/numbertheory/pow_mod.h
@@ -12,22 +12,7 @@
namespace Botan {
-/**
-* Modular Exponentiator Interface
-*/
-class BOTAN_PUBLIC_API(2,0) Modular_Exponentiator
- {
- public:
- virtual void set_base(const BigInt&) = 0;
- virtual void set_exponent(const BigInt&) = 0;
- virtual BigInt execute() const = 0;
- virtual Modular_Exponentiator* copy() const = 0;
-
- Modular_Exponentiator() = default;
- Modular_Exponentiator(const Modular_Exponentiator&) = default;
- Modular_Exponentiator & operator=(const Modular_Exponentiator&) = default;
- virtual ~Modular_Exponentiator() = default;
- };
+class Modular_Exponentiator;
/**
* Modular Exponentiator Proxy
@@ -93,7 +78,7 @@ class BOTAN_PUBLIC_API(2,0) Power_Mod
Usage_Hints hints = NO_HINTS,
bool disable_montgomery_arith = false);
Power_Mod(const Power_Mod&);
- virtual ~Power_Mod() = default;
+ virtual ~Power_Mod();
private:
mutable std::unique_ptr<Modular_Exponentiator> m_core;
};
diff --git a/src/lib/math/numbertheory/powm_fw.cpp b/src/lib/math/numbertheory/powm_fw.cpp
deleted file mode 100644
index c6ff169a1..000000000
--- a/src/lib/math/numbertheory/powm_fw.cpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
-* Fixed Window Exponentiation
-* (C) 1999-2007 Jack Lloyd
-*
-* Botan is released under the Simplified BSD License (see license.txt)
-*/
-
-#include <botan/internal/def_powm.h>
-#include <vector>
-
-namespace Botan {
-
-/*
-* Set the exponent
-*/
-void Fixed_Window_Exponentiator::set_exponent(const BigInt& e)
- {
- m_exp = e;
- }
-
-/*
-* Set the base
-*/
-void Fixed_Window_Exponentiator::set_base(const BigInt& base)
- {
- m_window_bits = Power_Mod::window_bits(m_exp.bits(), base.bits(), m_hints);
-
- m_g.resize(static_cast<size_t>(1) << m_window_bits);
- m_g[0] = 1;
- m_g[1] = m_reducer.reduce(base);
-
- for(size_t i = 2; i != m_g.size(); ++i)
- m_g[i] = m_reducer.multiply(m_g[i-1], m_g[1]);
- }
-
-/*
-* Compute the result
-*/
-BigInt Fixed_Window_Exponentiator::execute() const
- {
- const size_t exp_nibbles = (m_exp.bits() + m_window_bits - 1) / m_window_bits;
-
- BigInt x = 1;
-
- for(size_t i = exp_nibbles; i > 0; --i)
- {
- for(size_t j = 0; j != m_window_bits; ++j)
- x = m_reducer.square(x);
-
- const uint32_t nibble = m_exp.get_substring(m_window_bits*(i-1), m_window_bits);
-
- x = m_reducer.multiply(x, m_g[nibble]);
- }
- return x;
- }
-
-/*
-* Fixed_Window_Exponentiator Constructor
-*/
-Fixed_Window_Exponentiator::Fixed_Window_Exponentiator(const BigInt& n,
- Power_Mod::Usage_Hints hints)
- : m_reducer{Modular_Reducer(n)}, m_exp{}, m_window_bits{}, m_g{}, m_hints{hints}
- {}
-
-}
diff --git a/src/lib/math/numbertheory/powm_mnt.cpp b/src/lib/math/numbertheory/powm_mnt.cpp
deleted file mode 100644
index 99fbe9814..000000000
--- a/src/lib/math/numbertheory/powm_mnt.cpp
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
-* Montgomery Exponentiation
-* (C) 1999-2010,2012,2018 Jack Lloyd
-* 2016 Matthias Gierlings
-*
-* Botan is released under the Simplified BSD License (see license.txt)
-*/
-
-#include <botan/internal/def_powm.h>
-#include <botan/numthry.h>
-#include <botan/monty.h>
-#include <botan/internal/monty_exp.h>
-#include <botan/internal/rounding.h>
-
-namespace Botan {
-
-void Montgomery_Exponentiator::set_exponent(const BigInt& exp)
- {
- m_e = exp;
- }
-
-void Montgomery_Exponentiator::set_base(const BigInt& base)
- {
- size_t window_bits = Power_Mod::window_bits(m_e.bits(), base.bits(), m_hints);
- m_monty = monty_precompute(m_monty_params, m_mod_p.reduce(base), window_bits);
- }
-
-BigInt Montgomery_Exponentiator::execute() const
- {
- /*
- This leaks size of e via loop iterations, not possible to fix without
- breaking this API. Round up to avoid leaking fine details.
- */
- return monty_execute(*m_monty, m_e, round_up(m_e.bits(), 8));
- }
-
-Montgomery_Exponentiator::Montgomery_Exponentiator(const BigInt& mod,
- Power_Mod::Usage_Hints hints) :
- m_p(mod),
- m_mod_p(mod),
- m_monty_params(std::make_shared<Montgomery_Params>(m_p, m_mod_p)),
- m_hints(hints)
- {
- }
-
-}
diff --git a/src/lib/prov/pkcs11/p11_rsa.cpp b/src/lib/prov/pkcs11/p11_rsa.cpp
index 08f4115d1..1a760e1b2 100644
--- a/src/lib/prov/pkcs11/p11_rsa.cpp
+++ b/src/lib/prov/pkcs11/p11_rsa.cpp
@@ -15,7 +15,6 @@
#include <botan/pk_ops.h>
#include <botan/rng.h>
#include <botan/blinding.h>
-#include <botan/pow_mod.h>
namespace Botan {
@@ -124,9 +123,8 @@ class PKCS11_RSA_Decryption_Operation final : public PK_Ops::Decryption
RandomNumberGenerator& rng)
: m_key(key),
m_mechanism(MechanismWrapper::create_rsa_crypt_mechanism(padding)),
- m_powermod(m_key.get_e(), m_key.get_n()),
m_blinder(m_key.get_n(), rng,
- [ this ](const BigInt& k) { return m_powermod(k); },
+ [ this ](const BigInt& k) { return power_mod(k, m_key.get_e(), m_key.get_n()); },
[ this ](const BigInt& k) { return inverse_mod(k, m_key.get_n()); })
{
m_bits = m_key.get_n().bits() - 1;
@@ -164,7 +162,6 @@ class PKCS11_RSA_Decryption_Operation final : public PK_Ops::Decryption
const PKCS11_RSA_PrivateKey& m_key;
MechanismWrapper m_mechanism;
size_t m_bits = 0;
- Fixed_Exponent_Power_Mod m_powermod;
Blinder m_blinder;
};
diff --git a/src/lib/pubkey/dh/dh.cpp b/src/lib/pubkey/dh/dh.cpp
index 75b0db2f6..687032a69 100644
--- a/src/lib/pubkey/dh/dh.cpp
+++ b/src/lib/pubkey/dh/dh.cpp
@@ -1,13 +1,13 @@
/*
* Diffie-Hellman
-* (C) 1999-2007,2016 Jack Lloyd
+* (C) 1999-2007,2016,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/dh.h>
#include <botan/internal/pk_ops_impl.h>
-#include <botan/pow_mod.h>
+#include <botan/internal/monty_exp.h>
#include <botan/blinding.h>
namespace Botan {
@@ -86,20 +86,30 @@ class DH_KA_Operation final : public PK_Ops::Key_Agreement_with_KDF
DH_KA_Operation(const DH_PrivateKey& key, const std::string& kdf, RandomNumberGenerator& rng) :
PK_Ops::Key_Agreement_with_KDF(kdf),
m_p(key.group_p()),
- m_powermod_x_p(key.get_x(), m_p),
+ m_x(key.get_x()),
+ m_x_bits(m_x.bits()),
+ m_monty_p(key.get_group().monty_params_p()),
m_blinder(m_p,
rng,
[](const BigInt& k) { return k; },
- [this](const BigInt& k) { return m_powermod_x_p(inverse_mod(k, m_p)); })
+ [this](const BigInt& k) { return powermod_x_p(inverse_mod(k, m_p)); })
{}
size_t agreed_value_size() const override { return m_p.bytes(); }
secure_vector<uint8_t> raw_agree(const uint8_t w[], size_t w_len) override;
private:
- const BigInt& m_p;
+ BigInt powermod_x_p(const BigInt& v) const
+ {
+ const size_t powm_window = 4;
+ auto powm_v_p = monty_precompute(m_monty_p, v, powm_window);
+ return monty_execute(*powm_v_p, m_x, m_x_bits);
+ }
- Fixed_Exponent_Power_Mod m_powermod_x_p;
+ const BigInt& m_p;
+ const BigInt& m_x;
+ const size_t m_x_bits;
+ std::shared_ptr<const Montgomery_Params> m_monty_p;
Blinder m_blinder;
};
@@ -111,7 +121,7 @@ secure_vector<uint8_t> DH_KA_Operation::raw_agree(const uint8_t w[], size_t w_le
throw Invalid_Argument("DH agreement - invalid key provided");
v = m_blinder.blind(v);
- v = m_powermod_x_p(v);
+ v = powermod_x_p(v);
v = m_blinder.unblind(v);
return BigInt::encode_1363(v, m_p.bytes());
diff --git a/src/lib/pubkey/elgamal/elgamal.cpp b/src/lib/pubkey/elgamal/elgamal.cpp
index 6c2d6bccc..508ed1e8a 100644
--- a/src/lib/pubkey/elgamal/elgamal.cpp
+++ b/src/lib/pubkey/elgamal/elgamal.cpp
@@ -1,16 +1,15 @@
/*
* ElGamal
-* (C) 1999-2007,2018 Jack Lloyd
+* (C) 1999-2007,2018,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/elgamal.h>
#include <botan/internal/pk_ops_impl.h>
+#include <botan/internal/monty_exp.h>
#include <botan/keypair.h>
-#include <botan/reducer.h>
#include <botan/blinding.h>
-#include <botan/pow_mod.h>
namespace Botan {
@@ -63,7 +62,7 @@ bool ElGamal_PrivateKey::check_key(RandomNumberGenerator& rng,
if(!strong)
return true;
- return KeyPair::encryption_consistency_check(rng, *this, "EME1(SHA-256)");
+ return KeyPair::encryption_consistency_check(rng, *this, "OAEP(SHA-256)");
}
namespace {
@@ -86,15 +85,18 @@ class ElGamal_Encryption_Operation final : public PK_Ops::Encryption_with_EME
private:
const DL_Group m_group;
- Fixed_Base_Power_Mod m_powermod_y_p;
+ std::shared_ptr<const Montgomery_Exponentation_State> m_monty_y_p;
};
ElGamal_Encryption_Operation::ElGamal_Encryption_Operation(const ElGamal_PublicKey& key,
const std::string& eme) :
PK_Ops::Encryption_with_EME(eme),
- m_group(key.get_group()),
- m_powermod_y_p(key.get_y(), m_group.get_p())
+ m_group(key.get_group())
{
+ const size_t powm_window = 4;
+ m_monty_y_p = monty_precompute(key.get_group().monty_params_p(),
+ key.get_y(),
+ powm_window);
}
secure_vector<uint8_t>
@@ -110,7 +112,7 @@ ElGamal_Encryption_Operation::raw_encrypt(const uint8_t msg[], size_t msg_len,
const BigInt k(rng, k_bits);
const BigInt a = m_group.power_g_p(k, k_bits);
- const BigInt b = m_group.multiply_mod_p(m, m_powermod_y_p(k));
+ const BigInt b = m_group.multiply_mod_p(m, monty_execute(*m_monty_y_p, k, k_bits));
return BigInt::encode_fixed_length_int_pair(a, b, m_group.p_bytes());
}
@@ -130,8 +132,17 @@ class ElGamal_Decryption_Operation final : public PK_Ops::Decryption_with_EME
secure_vector<uint8_t> raw_decrypt(const uint8_t msg[], size_t msg_len) override;
private:
+ BigInt powermod_x_p(const BigInt& v) const
+ {
+ const size_t powm_window = 4;
+ auto powm_v_p = monty_precompute(m_monty_p, v, powm_window);
+ return monty_execute(*powm_v_p, m_x, m_x_bits);
+ }
+
const DL_Group m_group;
- Fixed_Exponent_Power_Mod m_powermod_x_p;
+ const BigInt& m_x;
+ const size_t m_x_bits;
+ std::shared_ptr<const Montgomery_Params> m_monty_p;
Blinder m_blinder;
};
@@ -140,11 +151,13 @@ ElGamal_Decryption_Operation::ElGamal_Decryption_Operation(const ElGamal_Private
RandomNumberGenerator& rng) :
PK_Ops::Decryption_with_EME(eme),
m_group(key.get_group()),
- m_powermod_x_p(key.get_x(), m_group.get_p()),
+ m_x(key.get_x()),
+ m_x_bits(m_x.bits()),
+ m_monty_p(key.get_group().monty_params_p()),
m_blinder(m_group.get_p(),
rng,
[](const BigInt& k) { return k; },
- [this](const BigInt& k) { return m_powermod_x_p(k); })
+ [this](const BigInt& k) { return powermod_x_p(k); })
{
}
@@ -164,7 +177,7 @@ ElGamal_Decryption_Operation::raw_decrypt(const uint8_t msg[], size_t msg_len)
a = m_blinder.blind(a);
- const BigInt r = m_group.multiply_mod_p(m_group.inverse_mod_p(m_powermod_x_p(a)), b);
+ const BigInt r = m_group.multiply_mod_p(m_group.inverse_mod_p(powermod_x_p(a)), b);
return BigInt::encode_1363(m_blinder.unblind(r), p_bytes);
}