Frontend-Backend split

Cargo.toml

@@ -2,4 +2,8 @@
 members = [
     "halo2",
     "halo2_proofs",
+    "halo2_frontend",
+    "halo2_middleware",
+    "halo2_backend",
+    "halo2_common",
 ]

halo2_backend/Cargo.toml

@@ -0,0 +1,65 @@
+[package]
+name = "halo2_backend"
+version = "0.3.0"
+authors = [
+    "Sean Bowe <[email protected]>",
+    "Ying Tong Lai <[email protected]>",
+    "Daira Hopwood <[email protected]>",
+    "Jack Grigg <[email protected]>",
+    "Privacy Scaling Explorations team",
+]
+edition = "2021"
+rust-version = "1.66.0"
+description = """
+Halo2 backend implementation.  This package implements the halo2 proof system which includes setup (key generation), proving and verifying.
+"""
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/zcash/halo2"
+documentation = "https://docs.rs/halo2_proofs"
+readme = "README.md"
+categories = ["cryptography"]
+keywords = ["halo", "proofs", "zkp", "zkSNARKs"]
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs", "--html-in-header", "katex-header.html"]
+
+[dependencies]
+backtrace = { version = "0.3", optional = true }
+ff = "0.13"
+group = "0.13"
+halo2curves = { version = "0.6.0", default-features = false }
+rand_core = { version = "0.6", default-features = false }
+tracing = "0.1"
+blake2b_simd = "1" # MSRV 1.66.0
+sha3 = "0.9.1"
+rand_chacha = "0.3"
+serde = { version = "1", optional = true, features = ["derive"] }
+serde_derive = { version = "1", optional = true}
+rayon = "1.8"
+halo2_middleware = { path = "../halo2_middleware" }
+halo2_common = { path = "../halo2_common" }
+
+[dev-dependencies]
+assert_matches = "1.5"
+criterion = "0.3"
+gumdrop = "0.8"
+proptest = "1"
+rand_core = { version = "0.6", default-features = false, features = ["getrandom"] }
+serde_json = "1"
+
+[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dev-dependencies]
+getrandom = { version = "0.2", features = ["js"] }
+
+[features]
+default = ["batch", "bits"]
+bits = ["halo2curves/bits"]
+gadget-traces = ["backtrace"]
+sanity-checks = []
+batch = ["rand_core/getrandom"]
+circuit-params = []
+cost-estimator = ["serde", "serde_derive"]
+derive_serde = ["halo2curves/derive_serde"]
+
+[lib]
+bench = false

halo2_backend/src/lib.rs

@@ -0,0 +1,10 @@
+pub mod plonk;
+
+// Internal re-exports
+pub use halo2_common::arithmetic;
+pub use halo2_common::circuit;
+pub use halo2_common::helpers;
+pub use halo2_common::multicore;
+pub use halo2_common::poly;
+pub use halo2_common::transcript;
+pub use halo2_common::SerdeFormat;