# `ExStorageServiceSdk.S3.SigV4a`
[🔗](https://github.com/gsmlg-opt/ex_storage_service/blob/v0.7.1/lib/ex_storage_service_sdk/s3/sigv4a.ex#L1)

AWS SigV4a request signing with credential-derived P-256 keys and OTP crypto.

# `presign_url`

Presigns a URL, retaining query duplicates and optional :headers required by the caller.

# `sign_headers`

Returns authentication headers; options follow SigV4, with :signing_region_set.

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*Consult [api-reference.md](api-reference.md) for complete listing*