The top little bit within the byte (also the top bit in the main nibble) is flipped for making 00000111, that's 0x07, as shown within the lower sample. Now, let's move on to implementing MD5 in code. Note that for practical uses, it is usually recommended to implement more robust https://kamerontzequ.blogocial.com/what-is-md5-technology-no-further-a-mystery-69301794