From 5ad59651bc2574be19a15b36862e512346509fcb Mon Sep 17 00:00:00 2001
From: York Jasper Niebuhr <yjnworkstation@gmail.com>
Date: Fri, 21 Nov 2025 19:15:14 +0100
Subject: [PATCH] BFV context API

---
 include/bfv.hpp | 78 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 74 insertions(+), 4 deletions(-)

diff --git a/include/bfv.hpp b/include/bfv.hpp
index 10488b8..d0e9961 100644
--- a/include/bfv.hpp
+++ b/include/bfv.hpp
@@ -1,15 +1,84 @@
 #pragma once
+#include <cstddef>
+#include <cstdint>
+#include <type_traits>
+#include <bit>
 
 namespace homcert::bfv {
 
+constexpr std::size_t VECSIZE = 8192;
+constexpr std::size_t PLAINMOD = 16760833; // 8192*2*1023+1 and prime
+
+template<std::size_t N, typename = void>
+struct smallest_uint;
+
+template<std::size_t N>
+struct smallest_uint<N, std::enable_if_t<(N <= UINT8_MAX)>> {
+	using type = std::uint8_t;
+};
+
+template<std::size_t N>
+struct smallest_uint<N, std::enable_if_t<(UINT8_MAX < N && N <= UINT16_MAX)>> {
+	using type = std::uint16_t;
+};
+
+template<std::size_t N>
+struct smallest_uint<N, std::enable_if_t<(UINT16_MAX < N && N <= UINT32_MAX)>> {
+	using type = std::uint32_t;
+};
+
+template<std::size_t N>
+struct smallest_uint<N, std::enable_if_t<(UINT32_MAX < N)>> {
+	using type = std::uint64_t;
+};
+
+struct plaintext {
+	using coefficient = typename smallest_uint<PLAINMOD>::type;
+
+	std::array<coefficient, VECSIZE> coefficients;
+
+	// Arithmetic...
+};
+
+using ciphertext = int;
+
+// Inheriting from context class allows pluggability of implementations (e.g. SEAL vs. GPU)
+
+class context {
+public:
+	context(const context& other) = delete;
+	context(context&& other) noexcept;
+	context& operator=(const context& other) = delete;
+	context& operator=(context&& other) noexcept;
+
+	context();
+	virtual ~context();
+
+	virtual bool allocate(ciphertext& ct) = 0;
+	virtual bool free(ciphertext ct) = 0;
+	virtual bool serialize(ciphertext ct, void* buf, std::size_t& n) = 0;
+	virtual bool deserialize(ciphertext ct, const void* buf, std::size_t n) = 0;
+	virtual bool encrypt(const plaintext& pt, ciphertext ct) = 0;
+	virtual bool decrypt(ciphertext ct, plaintext& pt) = 0;
+	virtual bool add_cipher_plain(ciphertext a, const plaintext& b, ciphertext res) = 0;
+	virtual bool add_cipher_cipher(ciphertext a, ciphertext b, ciphertext res) = 0;
+	virtual bool sub_cipher_plain(ciphertext a, const plaintext& b, ciphertext res) = 0;
+	virtual bool sub_cipher_cipher(ciphertext a, ciphertext b, ciphertext res) = 0;
+	virtual bool mul_cipher_plain(ciphertext a, const plaintext& b, ciphertext res) = 0;
+	virtual bool mul_cipher_cipher(ciphertext a, ciphertext b, ciphertext res) = 0;
+	virtual bool rot_cipher_rows(ciphertext ct, int r, ciphertext res) = 0;
+	virtual bool swap_cipher_rows(ciphertext ct, ciphertext res) = 0;
+	virtual bool noise_budget(ciphertext ct, std::size_t& budget) = 0;
+};
+
 /*
-TODO
-Device handles pluggability of implementations (e.g. SEAL vs. GPU)
-Operations are queued on device so the device can parallelize ops
+NOTE -> Implementations may defer operations or not wait for them to finish
+For example, GPU implementations may dispatch multiplications when they arive
+Additionally, a graph of running operations is maintained to handle data dependencies
+Only when data is required to actually be present (e.g. decrypt), does the implementation wait
 */
 
 /*
-No device class at all, just the context class which is handed to system as shared_ptr
 activate_context(std::shared_ptr<bfv::context> ctx) -> thread local pointer is set
 Raw ciphertext and plaintext classes always have the full 8192 coefficients (defined in context as static constexpr)
 bfv::vector<...>
@@ -32,6 +101,7 @@ Programs are defined TWICE
 	-> local stuff is executed
 	-> remote stuff is hosted (e.g. bootstrapping server)
 	-> defined once from each side (differ e.g. in the plaintext inputs etc.)
+	-> program base class may be used to handle context setting
 */
 
 }