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Process for Signing requests with StarSign

1

Calculate hash of HTTP Request Body

The digest algoritm to use is version specific. As of version 1 it is SHA256. The hash of the body are computed and compared “as-sent” and “as-recieved” which means there are no canonicalization of the body. Encoding must be UTF-8.hash(RequestBody)\text{hash}(\text{RequestBody})
2

Build signature payload

The payload is the string to be signed. It uses URL Encoding as representation with all values percent encoded. See payload specification. Example payload:
a=hmac-sha256&
d=GMuuPsaA4rCsGeMa56Ew4nu4ED79jkQ9kKS8UDUHYFv1&
id=clientID&
n=ETmr2tEpx691VS&
u=v1.SpaceParameterService%2FDescribeParameter&
t=20060102T150405Z
3

Compute HMAC signature

Compute the HMAC hash of the payload using the Client Secret.signature=HMAC(secret,payload)\text{signature} = \text{HMAC}(secret, payload)
4

Format Authorization header

Format the Authorization header. Base58 encode the HMAC hash and the payload using the BTC alphabet. The HeaderKey is version specific, as of version 1 it is starsign1.HeaderKey ∣∣ ’ ’ (space) ∣∣ Base58(signature) ∣∣ ’;’ ∣∣ Base58(payload)\small\text{HeaderKey} \ || \ \text{' ' (space)} \ || \ \text{Base58}(\text{signature}) \ || \ \text{';'} \ || \ \text{Base58}(\text{payload})
5

Set Authorization header to request and send it

Authorization: starsign1 3CAR2hUPT9[...];wMX3EtvWaZ[...]

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Signature Payload Parameters

The signature payload is metadata that gets signed and sent with the signature hash.
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a
string
required
HMAC algoritm constant is version specific, as of version 1 it is hmac-sha256.
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n
base58(BTC) encoded hash
required
Nonce must be at least 16 bytes and at most the same length as the client secret. Requests that reuse a previous nonce are denied.
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u
URL Path
required
URL Path of the request with any leading slash trimmed. Example v1.SpaceParameterService/DescribeParameter
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t
datetime
required
Time of signing the request. Time format is ISO 8601 (20060102T150405Z).
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d
base58(BTC) encoded hash
Hash digest value of the HTTP body. The digest algoritm is version specific, as of version 1 it is SHA256.
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b
datetime
The request is valid until and before the specified time. Time format is ISO 8601 (20060102T150405Z)

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Extending validity of requests

The StarSign signature scheme allows for setting a payload field named b for Before. It allows for extending the request validity into the future.
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