Predict the next base64 code in an enumnation attack on sequntial integers that have been turned to base64 code

1tL1K/nYW1Q= corresponds to 41154

sR4 ngjRepM= corresponds to 41155

“hint the above code does have a space”

the above codes are base64 and correspond to some string + orderids

I am doing this in .NET

If someone able to crack the series as I am trying to create this in custom code.

I want someone to test this and try to break it, so that I can see the flaw in my code.

The point is that I use the int codes in .Net with a preset string to generate the base64 codes. I am using this to prevent order enumeration attacks, yet have a small identifier instead of ints for order numbers. Do you think this is susceptible to attacks and whether you can work out what the “secret” is to producing the base64 codes to recognise orders, and enumerate them based on existing data I have provided.

I will place a bounty of 100 credits on this if someone can crack this.