Alphanumeric shellcode is similar to ascii shellcode in that it is used to bypass character filters and evade intrusion-detection during buffer overflow exploitation. This article documents alphanumeric code on multiple architectures, but primarily the 64 bit x86 architecture. Alphanumeric shellcode requires a basic understanding of bitwise math, assembly and shellcode.
You can download it from the following link: https://packetstormsecurity.com/files/download/113502/alpha.pdf
Source: https://packetstormsecurity.com/files/113502/Alphanumeric-Shellcode.html