topic Re: Unhashing a value in SAS for hash256 in SAS Programming

Unhashing a value in SAS for hash256

buddha_d — Thu, 27 May 2021 12:37:37 GMT

Dear Community,

Good morning. I want to unhash these dummy SSNs data. Could you please give me suggestions? I have the following sample program. I want to know how I can unhash the HASH_SSN variable in data two?

Thanks in advance,

data one;

input ID :$ SSN $9. ;
CARDS;
SAM 567457869
SMITH 897845678
SONY 003457896
;
RUN;

DATA TWO;
	SET ONE;
HASH_SSN=upcase(put(sha256(strip(SSN)||"e8pZqXwS0R"),$hex64.)) ;
RUN;

Re: Unhashing a value in SAS for hash256

LinusH — Thu, 27 May 2021 12:46:06 GMT

In a sense, hashing is some kind encryption. It's not meant to be reversed.

So before deciding to hashing values, you need to think of the consequences of doing so. Perhaps you need to store the original and hashed value pair somewhere (in a secure location if security is the reason to hash).

Re: Unhashing a value in SAS for hash256

mkeintz — Thu, 27 May 2021 14:27:13 GMT

As @LinusH said, you can't reverse the hash ~~code~~ function. If there were such a thing, what would be the point of the hash function in the first place? It would no longer be providing any sort of privacy protection.

But if you have your population of ssn's somewhere, you could reapply the hash function to create a map between the encrypted and original values. Then you could use that as a reverse lookup table.