What simple hash function can be implemented in VkScript?

Question

JavaScript

VKScript is a very stripped-down version of JavaScript that is executed on the VKontakte servers when the execute() API method is called. Supported, I quote:

• arithmetic operations
  
• logical operations
  
• creating arrays and lists ([X,Y])
  
• parseInt and parseDouble
  
• concatenation (+)
  
• if construct
  
• array filter by parameter (@.)
  
• API method calls, length parameter
  
• loops using the while statement
  
• Javascript methods: slice, push, pop, shift, unshift, splice, substr
  
• delete operator
  
• assigning array elements, for example: row.user.action = "test";
  

And no more than 25 VK API method calls. The number of rounds in cycles is also limited. Those. very, very truncated language.
It is necessary to protect a certain parameter transmitted through the client from forgery. It would be just great if I could check some kind of digital signature in this script. Those. on my server, I would calculate a certain hash from the parameter, and check it in this script.
Question : what hash-like function can be implemented in VKScript, and how?

Answer 1

It would be just great if I could check some kind of digital signature in this script. Those. on my server, I would calculate a certain hash from the parameter, and check it in this script.

It's not a digital signature, it's security through obscurity. A digital signature requires asymmetric encryption.
In my opinion, you can implement almost any hash function with this method set. If logical operations include bitwise. And if they do not include - you can implement them through arithmetic. Take something from simple ones, MD5, for example. Or even CRC32.