Added Comment to indicate _sd_alg claim

src/issuer.ts

@@ -4,6 +4,25 @@ import { IssueSDJWT } from './types.js';
 import { base64encode, combineSDJWT } from './helpers.js';
 import { IssueSDJWTError } from './errors.js';
 
+/**
+ * Issues a new Selectively Disclosable JWT (SD-JWT).
+ *
+ * Packs the provided payload based on the disclosureFrame,
+ * adds the `_sd_alg` claim (derived from the `hash.alg` option) to indicate
+ * the hashing algorithm used for disclosures.
+ * @param header The JWT header object.
+ * @param payload The JWT payload object containing the claims.
+ * @param disclosureFrame An object defining which claims in the payload should be made selectively disclosable.
+ * @param options Options for issuing the SD-JWT.
+ * @param options.signer An asynchronous function that takes the protected header and payload, and returns the signature.
+ * @param options.hash An object containing the hash algorithm information.
+ * @param options.hash.alg A string representing the hash algorithm used for disclosures (e.g., "sha-256"). This will be added as the _sd_alg claim.
+ * @param options.hash.callback An asynchronous function that takes data and returns its hash.
+ * @param options.generateSalt An optional function to generate a salt for disclosures. If not provided, a default salt generator will be used.
+ * @param options.cnf An optional object representing the confirmation method claim (e.g., for key binding).
+ * @returns A Promise that resolves to the compact representation of the SD-JWT (a string).
+ * @throws {IssueSDJWTError} If the signer or hasher callback is missing or not a function.
+ *  */
 export const issueSDJWT: IssueSDJWT = async (header, payload, disclosureFrame, { signer, hash, generateSalt, cnf }) => {
   if (!signer || typeof signer !== 'function') {
     throw new IssueSDJWTError('Signer function is required');