example of serials that has been encrypted. in reality we do not know the md5 hash, the serials, and the md5total.

serials:
CON-GRA-OEM-TSY-1.1
SOL-VED-OEM-ITY-1.1
OUO-BVI-OEM-OUS-1.1
LYK-NOW-OEM-HOW-1.1
TOD-OIT-OEM-NOW-1.1

encrypted text:
-144 -96 -147 -201 -152 -118 -163 -152 -120 -193 -182 -211 -119 -189 -147 -158 -211 -184 -141 -213 -194 -192 -148 -170 -131 -138 -205 -183 -86 -160 -144 -210 -130 -99 -179 -137 -214 -172 -157 -238 -159 -173 -142 -224 -156 -114 -171 -181 -161 -141 -126 -194 -137 -145 -118 -179 -177 -184 -189 -181 -140 -127 -122 -180 -113 -140 -125 -164 -136 -159 -186 -205 -185 -213 -106 -195 -146 -176 -129 -218 -110 -202 -154 -191 -126 -198 -134 -142 -142 -153 -102 -191 -83 -194 -130 -219 -163 -187 -171 -234

the md5 hash that we do not know:
cc460b0e0035f80845afb15f8b50dc55

the first md5total
223

with each md5total based off the last one and all the past chars,everything works out
ord('C')+12-223=-144
ord('O')+12-187=-96
ord('N')+4-229=-147 and so on so forth...