openvm_sha256_guest/
lib.rs

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1#![no_std]
2
3/// This is custom-0 defined in RISC-V spec document
4pub const OPCODE: u8 = 0x0b;
5pub const SHA256_FUNCT3: u8 = 0b100;
6pub const SHA256_FUNCT7: u8 = 0x1;
7
8/// The sha256 cryptographic hash function.
9#[inline(always)]
10pub fn sha256(input: &[u8]) -> [u8; 32] {
11    let mut output = [0u8; 32];
12    set_sha256(input, &mut output);
13    output
14}
15
16/// zkvm native implementation of sha256
17/// # Safety
18///
19/// The VM accepts the preimage by pointer and length, and writes the
20/// 32-byte hash.
21/// - `bytes` must point to an input buffer at least `len` long.
22/// - `output` must point to a buffer that is at least 32-bytes long.
23///
24/// [`sha2-256`]: https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf
25#[cfg(target_os = "zkvm")]
26#[inline(always)]
27#[no_mangle]
28extern "C" fn zkvm_sha256_impl(bytes: *const u8, len: usize, output: *mut u8) {
29    openvm_platform::custom_insn_r!(opcode = OPCODE, funct3 = SHA256_FUNCT3, funct7 = SHA256_FUNCT7, rd = In output, rs1 = In bytes, rs2 = In len);
30}
31
32/// Sets `output` to the sha256 hash of `input`.
33pub fn set_sha256(input: &[u8], output: &mut [u8; 32]) {
34    #[cfg(not(target_os = "zkvm"))]
35    {
36        use sha2::{Digest, Sha256};
37        let mut hasher = Sha256::new();
38        hasher.update(input);
39        output.copy_from_slice(hasher.finalize().as_ref());
40    }
41    #[cfg(target_os = "zkvm")]
42    {
43        zkvm_sha256_impl(input.as_ptr(), input.len(), output.as_mut_ptr() as *mut u8);
44    }
45}
openvm_sha256_guest/lib.rs

openvm_sha256_guest/
lib.rs
