How to properly make POST request - r

Question

I'm trying to make my first POST request to an API. For some reason, I always get status 403 in return. I suspect it's the signature that is being incorrectly generated. The api-key and client id is for sure correct.
My code
nonce <-as.integer(Sys.time())
post_message <- paste0(nonce, data_client.id, data_key) # data_client.id = client id # data_key = key
sha.message <- toupper(digest::hmac(data_secret, object = post_message, algo = 'sha256', serialize = TRUE))
url <- 'https://www.bitstamp.net/api/v2/balance/'
body = list('API-KEY' = data_key, 'nonce' = nonce, 'signature' = sha.message)
httr::POST(url, body = body, verbose())
Output
<- HTTP/1.1 403 Authentication Failed
I'm trying to access the Bitstamp API: https://www.bitstamp.net/api/?package=Rbitcoin&version=0.9.2
All private API calls require authentication. For a successful
authentication you need to provide your API key, a signature and a
nonce parameter.
API KEY
To get an API key, go to "Account", "Security" and then "API Access".
Set permissions and click "Generate key".
NONCEN
once is a regular integer number. It must be increased with every
request you make. Read more about it here. Example: if you set nonce
to 1 in your first request, you must set it to at least 2 in your
second request. You are not required to start with 1. A common
practice is to use unix time for that parameter.
SIGNATURE
Signature is a HMAC-SHA256 encoded message containing nonce, customer
ID (can be found here) and API key. The HMAC-SHA256 code must be
generated using a secret key that was generated with your API key.
This code must be converted to it's hexadecimal representation (64
uppercase characters).

Answer 1

I'm not sure if your question is still standing, but based on your code, I managed to get it working. In fact, the main problem is in the body, the API documentation shows it expects 'key' instead of 'API-KEY'.
Also, serialize should be FALSE instead of TRUE.
At the moment this works (but the API may change):
nonce <-as.integer(Sys.time())
post_message <- paste0(nonce, data_client.id, data_key) # data_client.id = client id # data_key = key
sha.message <- toupper(digest::hmac(data_secret, object = post_message, algo = 'sha256', serialize = FALSE))
url <- 'https://www.bitstamp.net/api/v2/balance/'
body = list('key' = data_key, 'nonce' = nonce, 'signature' = sha.message)
httr::POST(url, body = body, verbose())