TypeError: Failed to execute 'sign' on 'SubtleCrypto': EcdsaParams: hash: Missing or not an AlgorithmIdentifier

Chromium's text is above (for `verify` the method name changes); Safari/WebKit: "Member EcdsaParams.hash is required and must be an instance of (object or DOMString)"; Firefox reports a generic `SyntaxError` ("An invalid or illegal string was specified").

WebCrypto SubtleCrypto.sign / verify with ECDSA — algorithm parameter without hash (Chromium / WebKit)

What it means

ECDSA in WebCrypto takes the hash function per operation, not per key: `sign` and `verify` need `{ name: "ECDSA", hash: "SHA-256" }`. The call passed an algorithm object without `hash` — usually the `{ name, namedCurve }` object from key generation — so the browser rejected the parameters before signing. (RSA keys are the opposite: their hash is fixed at import time.) A misspelled hash such as `"SHA256"` fails with a `NotSupportedError` about an unrecognized name instead.

Why it happens

• The key-generation parameters reused for sign/verify

  common

  Storing one `ALG = { name: "ECDSA", namedCurve: "P-256" }` constant and passing it everywhere works for `generateKey` and `importKey`, but `sign` needs `hash`.

• Hash name spelled the JOSE or OpenSSL way

  common

  WebCrypto names are `SHA-256`, `SHA-384`, `SHA-512` (with the hyphen). `SHA256`, `sha256` with no hyphen or `ES256` are unrecognized.

• Expecting the key to carry the hash

  occasional

  Code ported from RSA (`RSASSA-PKCS1-v1_5` keys have `hash` in their import parameters) assumes ECDSA keys do too; they do not.

How to fix it

1. 1.

   Keep key parameters and operation parameters separate

   Define one object for key creation and one for signing. For JWT ES256/ES384/ES512, use SHA-256/384/512 with P-256/384/521 respectively.

   const KEY_ALG = { name: "ECDSA", namedCurve: "P-256" };   // generateKey / importKey
   const SIGN_ALG = { name: "ECDSA", hash: "SHA-256" };        // sign / verify (ES256)
   
   const pair = await crypto.subtle.generateKey(KEY_ALG, false, ["sign", "verify"]);
   const signature = await crypto.subtle.sign(SIGN_ALG, pair.privateKey, data);   // 64 bytes, raw r||s
   const ok = await crypto.subtle.verify(SIGN_ALG, pair.publicKey, signature, data);

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