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SIGN Parameter Calculation

The value of the sign field is a message digest, expressed as a string of sixty-four hexadecimal digits. It is constructed by performing a hashing calculation on a string built up by concatenating the following fields:

  • merchant_id
  • transaction_id
  • the uppercase MD5 value of the ASCII equivalent of the secret word submitted in the Settings > Developer Settings > API/MQI/GSR/CVT Management section of your online Skrill account
  • amount
  • currency

The default algorithm for hashing these parameters is HMAC SHA-256. It requires a secret key to complete the hash. In our case, that key is, once again, the MD5 value of the ASCII equivalent of the secret word (lowercase).

Example (HMAC SHA-256)

FieldValue
merchant_id299202295
transaction_idfrn123merid
MD5 hash of secret word (uppercase)EE38B95C14D6CC07F48EF550C4474EE3
amount20.45
currencyGBP
concatenated value299202295frn123meridEE38B95C14D6CC07F48EF550C4474EE320.45GBP
secret key for the encryption (MD5 hash of secret word lowercase)ee38b95c14d6cc07f48ef550c4474ee3
sign1F4ACCA3FED7681C2C9F645DDF3210A88A5A4F072FEF5DF432CF3BB053136D87