Reversing an encryption routine in asm

Question

I am having a really hard time trying to reverse this encryption routine, and honestly understanding it as well. Any help would be appreciated.

encrypt_22:
        push  ebp                             //  save call site base pointer to the stack
            mov   ebp, esp                    //  new stack frame base
            // // // // // // // // // // // ///
            push  edi                         //  free up register
            push  ecx                         //  copy original character and free up register
            and byte ptr[eax], 0x0F           //  substract 12 bits from the value of og Ekey
            cmp   byte ptr[eax], 0x00         //  condition, Ekey != 0
            jnz   x22                         //  if condition true jump to x22
            mov   edi, 0x02                   //  store 2 in here
            jmp   z22                         //  if condition, Ekey = 0, jump to z22
            x22 : movzx edi, byte ptr[eax]    //  start counter
            z22 : add   byte ptr[eax], 0x0A   //  add to Ekey
            pop   eax                         //  get original character
            y22 : dec   eax                   //  mangle Ekey
            dec   edi                         //  condition, if edi = 0; edi--
            jnz   y22                         //  jump to y22
            not al                            //  mangle by flipping 
            dec   eax                         //  mangle by substracting by one 
            pop   edi                         //  restore Ekey      
            xor al, 0x0A                      //  substract by ten to mangle
            mov   edx, eax                    //  put mangled result in output
            // // // // // // // // // // // ///
            mov   esp, ebp                    //  point stack pointer at base pointer
            pop   ebp                         //  restore call site base pointer
            ret   8                           //  return and scrub the stack
    }