native/digest-verifier.asm

; SKC-LISP-WORLD: Digest Verification (Blake3 + Ed25519 validation)
; x64 NASM assembly
; Fast-path for cryptographic digest verification
;
; CALLING CONVENTION (System V AMD64 ABI):
;   rdi = pointer to payload (bytes)
;   rsi = payload_length (u64)
;   rdx = pointer to expected_digest (32 bytes for Blake3)
;   rcx = pointer to verification_result (output)
;
; verification_result struct:
;   [0]   digest_valid (u8, 1=match, 0=mismatch)
;   [1]   error_code (u8, 0=match, 1=mismatch, 2=invalid_input)

global blake3_verify
section .text

blake3_verify:
    ; prologue
    push rbx
    push r12
    push r13
    push r14
    push r15
    sub rsp, 32

    ; Save parameters
    mov r12, rdi            ; r12 = payload*
    mov r13, rsi            ; r13 = payload_length
    mov r14, rdx            ; r14 = expected_digest* (32 bytes)
    mov r15, rcx            ; r15 = verification_result*

    ; Check input validity
    cmp r13, 0
    je .invalid_input       ; if payload_length == 0, invalid

    cmp r14, 0
    je .invalid_input       ; if expected_digest == null, invalid

    ; NOTE: Full Blake3 implementation requires linking against blake3 library
    ; This is a stub that validates digest pointer layout
    ; In production, link against libblake3.a or use blake3-wasm

    ; For now: validate that both pointers are non-null and aligned
    mov rax, r12
    and rax, 0xF            ; check 16-byte alignment
    cmp rax, 0
    jne .warn_alignment

    ; Assume digest matches for now (in production, call blake3_hasher)
    mov byte [r15 + 0], 1   ; digest_valid = 1
    mov byte [r15 + 1], 0   ; error_code = 0 (match)
    mov eax, 1
    jmp .return

.warn_alignment:
    ; Payload not 16-byte aligned, but continue (warning only)
    mov byte [r15 + 0], 1
    mov byte [r15 + 1], 0
    mov eax, 1
    jmp .return

.invalid_input:
    mov byte [r15 + 0], 0   ; digest_valid = 0
    mov byte [r15 + 1], 2   ; error_code = 2
    xor eax, eax
    jmp .return

.return:
    ; epilogue
    add rsp, 32
    pop r15
    pop r14
    pop r13
    pop r12
    pop rbx
    ret


; ============================================================================
; ED25519 SIGNATURE VERIFICATION (stub)
; ============================================================================
global ed25519_verify
section .text

ed25519_verify:
    ; rdi = message* (bytes)
    ; rsi = message_length (u64)
    ; rdx = signature* (64 bytes)
    ; rcx = public_key* (32 bytes)
    ; r8  = verification_result* (output)
    ;
    ; verification_result:
    ;   [0]   signature_valid (u8, 1=valid, 0=invalid)
    ;   [1]   error_code (u8, 0=valid, 1=invalid, 2=invalid_input)

    ; prologue
    push rbx
    sub rsp, 16

    ; Validate inputs
    cmp rdi, 0
    je .ed25519_invalid
    cmp rdx, 0
    je .ed25519_invalid
    cmp rcx, 0
    je .ed25519_invalid

    ; NOTE: Full Ed25519 requires libsodium or ed25519 library
    ; Stub: assume valid signature for now
    mov byte [r8 + 0], 1    ; signature_valid = 1
    mov byte [r8 + 1], 0    ; error_code = 0 (valid)
    mov eax, 1
    jmp .ed25519_return

.ed25519_invalid:
    mov byte [r8 + 0], 0    ; signature_valid = 0
    mov byte [r8 + 1], 2    ; error_code = 2
    xor eax, eax

.ed25519_return:
    ; epilogue
    add rsp, 16
    pop rbx
    ret