import type { SampledSpan, ScoreResponsesResult } from './types.js';
/**
 * Derive the challenge seed. The preimage is the RFC 8785 JCS
 * canonicalization of an object carrying the four bound fields, so the
 * component boundaries are unambiguous: presentation_digest is a
 * distinct JSON member (null when absent), never foldable into the
 * nonce. An earlier concatenation preimage let a null-presentation
 * record with nonce = P || N derive the same seed as a P-presentation
 * record with nonce N; the structured preimage closes that.
 */
export declare function deriveSeed(contentDigest: string, presentationDigestOrNull: string | null, nonce: string, version: string): string;
/**
 * Sample `n` spans of `spanLen` code points from `sourceText` at
 * distinct positions determined by `seed` (algorithm span_sample_v1).
 *
 * The source is split into code points via Array.from, so astral
 * characters (emoji) count as one position each and spans never split
 * a surrogate pair. With L code points the position range is
 * L - spanLen + 1. Throws when spanLen or n is not a positive integer,
 * when the source is shorter than spanLen code points, or when n
 * exceeds the position range.
 */
export declare function sampleSpans(sourceText: string, seed: string, n: number, spanLen: number): SampledSpan[];
/**
 * Commit to span texts: "sha256:" + sha256hex(UTF-8 of each span
 * text), in the given (sampling) order.
 */
export declare function commitSpans(spanTexts: readonly string[]): string[];
/**
 * Score responses against span texts under exact_match_v1: exact
 * string equality per index. Throws when the arrays differ in length;
 * a missing response is a protocol error, not a miss.
 */
export declare function scoreResponses(spanTexts: readonly string[], responses: readonly string[]): ScoreResponsesResult;
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