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LabeledExpand.md

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Function: LabeledExpand()

LabeledExpand(KDF, suite_id, prk, label, info, L): Promise<Uint8Array>

Performs labeled expansion for two-stage KDFs.

This function implements the LabeledExpand operation as specified in the HPKE specification for use with two-stage KDFs. It constructs a labeled info string by concatenating:

  • The desired output length as a 2-byte encoding
  • The version string "HPKE-v1"
  • The suite identifier (suite_id)
  • The label
  • Additional info context

The labeled info is then passed to the KDF's Expand function along with the pseudorandom key to produce L bytes of output keying material. This ensures domain separation between different uses of the KDF in HPKE.

Parameters

Parameter Type
KDF Pick<KDF, "Expand">
suite_id Uint8Array
prk Uint8Array
label Uint8Array
info Uint8Array
L number

Returns

Promise<Uint8Array>

See

LabeledExpand