SHA256 breaking personalization strings in email

Question

We are currently using this code block in an email

%%[
VAR @email, @customer_no, @secret, @url, @hash
SET @email = "%%email%%"
SET @customer_no = "%%customer_no%%"
SET @secret = "<secretkey>"
SET @hash = SHA256(Concat(@email,@customer_no,@secret))
SET @url = Concat("<CompanyURL>?a=",@email,"&amp;c=",@customer_no,"&amp;h=",@hash)
]%%

And vardumping with

%%=v(@email)=%%
%%=v(@customer_no)=%%
%%=v(@secret)=%%
%%=v(@hash)=%%

The url that we get has both the email address and the customer number correctly, but the hash is wrong. Looking at the vardump, the email and customer_no were returning "%%email%%" and "%%customer_no%%" respectively instead of the personalizations. The hash should be "emailcustomer_nosecret" no spaces between.

Answer 1

You're mixing inline and block AMPscript. No need for the double-percent notation in your block:

%%[

VAR @email, @customer_no, @secret, @url, @hash
SET @email = AttributeValue("email")
SET @customer_no = AttributeValue("customer_no")
SET @secret = "<secretkey>"
SET @hash = SHA256(Concat(@email,@customer_no,@secret))
SET @url = Concat("<CompanyURL>a=", @email, "&amp;c=", @customer_no, "&amp;h=", @hash)

]%%

Answer 2

I'm still not entirely sure why the personalization strings didn't work inside the SHA256 function, but replacing the personalization strings with Lookups made it work.

Final Code:

%%[
VAR @email, @customer_no, @secret, @url, @hash
SET @email = Lookup("DEtest","email","email",_SubscriberKey)
SET @customer_no = Lookup("DEtest","customer_no","email",_SubscriberKey)
SET @secret = "<SECRET KEY>"
SET @hash = SHA256(Concat(@email,@customer_no,@secret))
SET @url = Concat("<URL>a=",@email,"&amp;c=",@customer_no,"&amp;h=",@hash)
]%%