Add sphincs+ sha2 signature generator

Makefile

@@ -63,3 +63,7 @@ sphincs-prove:
 		--proofs_dir $(TARGET_DIR) \
 		--proof-format cairo-serde \
 		--verify
+
+sphincs-args:
+	cd packages/sphincs-plus/scripts && cargo +nightly run --release --example generate_cairo_data \
+		> ../tests/data/sha2_simple_128s.json

packages/sphincs-plus/scripts/.gitignore

@@ -0,0 +1 @@
+target/

packages/sphincs-plus/scripts/Cargo.toml

@@ -0,0 +1,66 @@
+[package]
+name = "pqc_sphincsplus"
+version = "0.2.0"
+edition = "2021"
+authors = ["Mitchell Berry <foss@mitchellberry.com>"]
+description = "Sphincs+ is a post-quantum signature scheme"
+readme = "readme.md"
+repository = "https://github.com/Argyle-Software/pqc_sphincsplus"
+license = "MIT OR Apache-2.0"
+categories = ["algorithms", "cryptography", "no-std"]
+keywords = ["sphincsplus", "sphincs+", "sphincs", "signature", "post-quantum"]
+exclude = ["tests/KAT/", ".github" ]
+
+[dependencies]
+rand = "0.8.5"
+sha3 = { version = "0.10.8", optional = true }
+hex = "0.4"
+
+# Rename sha2 crate
+[dependencies.sha256]
+package = "sha2"
+version = "0.10.7"
+features = ["compress"]
+optional = true
+
+[dev-dependencies]
+pqc_core = {version = "0.3.0", features = ["load"]}
+
+# Must enable only one from each of the groups below
+# otherwise library will throw a compilation error
+[features]
+default = ["sha2", "s128", "simple"]
+
+### Hash ###
+haraka = []
+sha2 = ["sha256"]
+shake = ["sha3"]
+
+### Security level ###
+# Considered equivalent to 128, 192 and 256 bit
+# NIST levels 1, 3 & 5 respectively
+# Additionally there is a fast signature mode (f)
+# and a small signature mode (s)
+# See the readme and benchmarks for comparison. 
+f128 = []
+f192 = []
+f256 = []
+s128 = []
+s192 = []
+s256 = []
+
+### Tree Hash ###
+# SPHINCS+ splits the signatures schemes into a simple and a robust 
+# variant for each choice of hash function. The robust variant is 
+# comes with all the conservative security guarantees given in SPHNICS. 
+# The simple variants are pure random oracle instantiations. These 
+# instantiations achieve about a factor three speed-up 
+# compared to the robust counterparts. This comes at the 
+# cost of a purely heuristic security argument.
+simple = []
+robust = []
+
+# Exposes inner api methods
+# Do not use except for running test vectors
+KAT = ["sha2"]
+