Blowfish CBC Mode for MASM

Blowfish_EncryptCBC proc dataIn:DWORD, dataOut:DWORD, dataLen:DWORD, ivPtr:DWORD
    LOCAL ivHI:DWORD
    LOCAL ivLO:DWORD
    LOCAL decryptSize:DWORD

    ;load IV into local vars
    mov eax, ivPtr
    push [eax]
    pop ivHI
    push [eax+4]
    pop ivLO


    ;calculate number of blocks
    mov eax, dataLen
    sar eax, 3
    xchg eax, ecx
    mov esi, dataIn
    mov edi, dataOut
    xor ebx,ebx

    .while ecx != 0

        ;xor input
        mov eax, ivHI
        mov edx, [esi+ebx]
        bswap edx
        xor edx,eax
        mov [esi+ebx], edx

        mov eax, ivLO
        mov edx, [esi+ebx+4]
        bswap edx
        xor edx,eax
        mov [esi+ebx+4], edx

        lea edx, [esi +ebx]
        push edx
        lea edx, [edi +ebx]
        push edx

        call Blowfish_Encrypt

        ;update CV
        push [edi+ebx]
        pop ivHI

        push [edi+ebx+4]
        pop ivLO

        ;adjust output
        mov eax, [edi+ebx]
        bswap eax
        mov [edi+ebx], eax

        mov eax, [edi+ebx +4]
        bswap eax
        mov [edi+ebx +4], eax

        add ebx, 8
        dec ecx
    .endw

    mov eax, dataLen    ;check for valid size
    and eax, 80000007h
    .if eax > 0
        lea eax, ivLO
        ;flip them here!
        push ivLO
        push ivHI
        pop ivLO
        pop ivHI
        invoke Blowfish_Encrypt,eax,eax
        mov esi, dataIn     ;esi holds pointer to encrypted data
        mov edi, dataOut    ;edi holds pointer to decrypt buffer

        mov edx, [esi+ebx]      ;load decrypted result HI
        bswap edx
        xor edx, ivLO           ;XOR with IV HI
        bswap edx
        mov [edi+ebx], edx      ;store result HI

        mov edx, [esi+ebx +4]   ;load decrypted result LO
        bswap edx
        xor edx, ivHI           ;XOR with IV LO
        bswap edx
        mov [edi+ebx +4], edx;store result LO
    .endif

    ret
Blowfish_EncryptCBC endp


Blowfish_DecryptCBC proc dataIn:DWORD, dataOut:DWORD, dataLen:DWORD, ivPtr:DWORD
    LOCAL ivHI:DWORD
    LOCAL ivLO:DWORD
    LOCAL ivNextHI:DWORD
    LOCAL ivNextLO:DWORD
    LOCAL decryptSize:DWORD

    mov eax, ivPtr
    push [eax]
    pop ivHI
    push [eax + 4]
    pop ivLO

    mov eax, dataLen    ;check for valid size

    sar eax, 3

    xchg eax, ecx       ;move number of chunks to ECX
    mov esi, dataIn     ;esi holds pointer to encrypted data
    mov edi, dataOut    ;edi holds pointer to decrypt buffer
    xor ebx,ebx         ;current offset

    .while ecx != 0
        lea eax, [esi+ebx]      ;get source offset
        push ecx                ;save ECX
        mov ecx, [eax]
        bswap ecx
        push ecx
        pop ivNextHI            ;save next IV HI
        mov ecx, [eax+4]
        bswap ecx
        push ecx
        pop ivNextLO            ;save next IV LO
        pop ecx                 ;restore ECX
        push eax                ;push source offset
        push ecx                ;save ecx
        mov ecx, [eax]
        bswap ecx
        mov [eax], ecx
        mov ecx, [eax+4]
        bswap ecx
        mov [eax+4], ecx
        pop ecx                 ;restore ECX
        lea eax, [edi+ebx]      ;load dest offset
        push eax                ;push dest offset

        call Blowfish_Decrypt   ;decrypt

        mov edx, [edi+ebx]      ;load decrypted result HI
        xor edx, ivHI           ;XOR with IV HI
        bswap edx
        mov [edi+ebx], edx      ;store result HI

        mov edx, [edi+ebx +4]   ;load decrypted result LO
        xor edx, ivLO           ;XOR with IV LO
        bswap edx
        mov [edi+ebx +4], edx;store result LO

        push ivNextLO
        pop ivLO
        push ivNextHI
        pop ivHI

        add ebx, 8              ;increment pointer by 8
        dec ecx                 ;decrement remaining blocks
    .endw

    mov eax, dataLen    ;check for valid size
    and eax, 80000007h
    .if eax > 0
        lea eax, ivLO
        ;flip them here!
        push ivLO
        push ivHI
        pop ivLO
        pop ivHI
        invoke Blowfish_Encrypt,eax,eax
        mov esi, dataIn     ;esi holds pointer to encrypted data
        mov edi, dataOut    ;edi holds pointer to decrypt buffer

        mov edx, [esi+ebx]      ;load decrypted result HI
        bswap edx
        xor edx, ivLO           ;XOR with IV HI
        bswap edx
        mov [edi+ebx], edx      ;store result HI

        mov edx, [esi+ebx +4]   ;load decrypted result LO
        bswap edx
        xor edx, ivHI           ;XOR with IV LO
        bswap edx
        mov [edi+ebx +4], edx;store result LO
    .endif


    ret
Blowfish_DecryptCBC endp