diff --git a/benchmark/crypto/prepare-asymmetric-key.js b/benchmark/crypto/prepare-asymmetric-key.js
new file mode 100644
index 000000000000..dd536c3f451c
--- /dev/null
+++ b/benchmark/crypto/prepare-asymmetric-key.js
@@ -0,0 +1,178 @@
+'use strict';
+
+const common = require('../common.js');
+const crypto = require('node:crypto');
+const fs = require('node:fs');
+const path = require('node:path');
+const { pathToFileURL } = require('node:url');
+const { hasOpenSSL, isBoringSSL } = require('../../test/common/crypto.js');
+
+const inputs = [
+  'public-keyobject', 'public-keyobject-wrapped', 'public-pem-buffer-wrapped',
+  'private-keyobject', 'private-keyobject-wrapped',
+  'private-pem-string', 'private-pem-buffer', 'private-pem-arraybuffer',
+  'private-pem-string-wrapped', 'private-pem-buffer-wrapped', 'private-pem-arraybuffer-wrapped',
+  'private-jwk',
+  'public-der-pkcs1-bytes', 'private-der-pkcs1-bytes', 'private-pem-pkcs8-bytes',
+  'private-der-pkcs8-bytes', 'private-der-pkcs8-base64', 'private-der-pkcs8-hex',
+  'public-der-spki-bytes', 'private-der-sec1-bytes',
+  'raw-public-ec-buffer', 'raw-public-ed25519-buffer',
+  'raw-private-ec-buffer', 'raw-private-ec-arraybuffer', 'raw-private-ed25519-buffer',
+  'pem-passphrase-absent', 'pem-passphrase-empty', 'pem-passphrase-string',
+  'pem-passphrase-base64', 'pem-passphrase-buffer', 'pem-passphrase-arraybuffer',
+  'file-passphrase-absent', 'file-passphrase-string', 'file-direct',
+  'provider-passphrase-absent', 'provider-passphrase-absent-properties',
+  'provider-passphrase-empty', 'provider-passphrase-string', 'provider-passphrase-base64',
+  'provider-passphrase-buffer', 'provider-passphrase-arraybuffer', 'provider-direct',
+];
+
+if (hasOpenSSL(3, 5) || isBoringSSL)
+  inputs.push('raw-seed-ml-dsa-44-buffer');
+
+const bench = common.createBenchmark(main, {
+  input: inputs,
+  context: ['consume-public', 'consume-private', 'create-public'],
+  n: [1e6],
+}, {
+  flags: ['--expose-internals'],
+  combinationFilter({ input, context }) {
+    if (input === 'private-keyobject' || input === 'private-keyobject-wrapped')
+      return true;
+    if (input.startsWith('public-') || input.startsWith('raw-public-'))
+      return context === 'consume-public';
+    return context === 'consume-private';
+  },
+});
+
+function main({ input, context, n }) {
+  const {
+    prepareAsymmetricKey,
+    kConsumePublic,
+    kConsumePrivate,
+    kCreatePublic,
+  } = require('internal/crypto/keys');
+  const ctx = {
+    'consume-public': kConsumePublic,
+    'consume-private': kConsumePrivate,
+    'create-public': kCreatePublic,
+  }[context];
+  const fixtureDir = path.resolve(__dirname, '../../test/fixtures/keys');
+  const privateKeyPath = path.join(fixtureDir, 'rsa_private_2048.pem');
+  const privateKey = crypto.createPrivateKey(fs.readFileSync(privateKeyPath));
+  const publicKey = crypto.createPublicKey(privateKey);
+  const pem = privateKey.export({ format: 'pem', type: 'pkcs8' });
+  const buffer = Buffer.from(pem);
+  const arraybuffer = Uint8Array.from(buffer).buffer;
+  const fileURL = pathToFileURL(privateKeyPath);
+  const providerURL = new URL('pkcs11:object=signing-key;type=private');
+  const passphrase = Buffer.from('password');
+
+  let key;
+  switch (input) {
+    case 'public-keyobject': key = publicKey; break;
+    case 'public-keyobject-wrapped': key = { key: publicKey }; break;
+    case 'public-pem-buffer-wrapped':
+      key = { key: Buffer.from(publicKey.export({ format: 'pem', type: 'spki' })) };
+      break;
+    case 'private-keyobject': key = privateKey; break;
+    case 'private-keyobject-wrapped': key = { key: privateKey }; break;
+    case 'private-pem-string': key = pem; break;
+    case 'private-pem-buffer': key = buffer; break;
+    case 'private-pem-arraybuffer': key = arraybuffer; break;
+    case 'private-pem-string-wrapped': key = { key: pem }; break;
+    case 'private-pem-buffer-wrapped': key = { key: buffer }; break;
+    case 'private-pem-arraybuffer-wrapped': key = { key: arraybuffer }; break;
+    case 'private-jwk': key = { key: privateKey.export({ format: 'jwk' }), format: 'jwk' }; break;
+    case 'public-der-pkcs1-bytes': key = { key: publicKey, format: 'der', type: 'pkcs1' }; break;
+    case 'private-der-pkcs1-bytes': key = { key: privateKey, format: 'der', type: 'pkcs1' }; break;
+    case 'private-pem-pkcs8-bytes': key = { key: privateKey, format: 'pem', type: 'pkcs8' }; break;
+    case 'private-der-pkcs8-bytes': key = { key: privateKey, format: 'der', type: 'pkcs8' }; break;
+    case 'private-der-pkcs8-base64':
+      key = { key: privateKey, format: 'der', type: 'pkcs8', encoding: 'base64' };
+      break;
+    case 'private-der-pkcs8-hex':
+      key = { key: privateKey, format: 'der', type: 'pkcs8', encoding: 'hex' };
+      break;
+    case 'public-der-spki-bytes': key = { key: publicKey, format: 'der', type: 'spki' }; break;
+    case 'private-der-sec1-bytes':
+      key = {
+        key: crypto.createPrivateKey(fs.readFileSync(path.join(fixtureDir, 'ec_p256_private.pem'))),
+        format: 'der', type: 'sec1',
+      };
+      break;
+    case 'raw-public-ec-buffer':
+    case 'raw-public-ed25519-buffer':
+    case 'raw-private-ec-buffer':
+    case 'raw-private-ec-arraybuffer':
+    case 'raw-private-ed25519-buffer': {
+      const asymmetricKeyType = input.includes('-ec-') ? 'ec' : 'ed25519';
+      const fixture = asymmetricKeyType === 'ec' ? 'ec_p256_private.pem' : 'ed25519_private.pem';
+      let rawKey = crypto.createPrivateKey(fs.readFileSync(path.join(fixtureDir, fixture)));
+      const format = input.startsWith('raw-public-') ? 'raw-public' : 'raw-private';
+      if (format === 'raw-public') rawKey = crypto.createPublicKey(rawKey);
+      const bytes = rawKey.export({ format });
+      key = {
+        key: input.endsWith('-arraybuffer') ? Uint8Array.from(bytes).buffer : bytes,
+        format,
+        asymmetricKeyType,
+        namedCurve: asymmetricKeyType === 'ec' ? 'prime256v1' : undefined,
+      };
+      break;
+    }
+    case 'raw-seed-ml-dsa-44-buffer': {
+      const seedKey = crypto.createPrivateKey(
+        fs.readFileSync(path.join(fixtureDir, 'ml_dsa_44_private_seed_only.pem')));
+      key = { key: seedKey.export({ format: 'raw-seed' }), format: 'raw-seed', asymmetricKeyType: 'ml-dsa-44' };
+      break;
+    }
+    case 'pem-passphrase-absent': key = { key: privateKey }; break;
+    case 'pem-passphrase-empty': key = { key: privateKey, passphrase: '' }; break;
+    case 'pem-passphrase-string': key = { key: privateKey, passphrase: 'password' }; break;
+    case 'pem-passphrase-base64':
+      key = { key: privateKey, passphrase: passphrase.toString('base64'), encoding: 'base64' };
+      break;
+    case 'pem-passphrase-buffer': key = { key: privateKey, passphrase }; break;
+    case 'pem-passphrase-arraybuffer':
+      key = { key: privateKey, passphrase: Uint8Array.from(passphrase).buffer };
+      break;
+    case 'file-passphrase-absent': key = { key: fileURL }; break;
+    case 'file-passphrase-string': key = { key: fileURL, passphrase: 'password' }; break;
+    case 'file-direct': key = fileURL; break;
+    case 'provider-passphrase-absent': key = { key: providerURL }; break;
+    case 'provider-passphrase-absent-properties': key = { key: providerURL, properties: 'provider=default' }; break;
+    case 'provider-passphrase-empty': key = { key: providerURL, passphrase: '' }; break;
+    case 'provider-passphrase-string': key = { key: providerURL, passphrase: 'password' }; break;
+    case 'provider-passphrase-base64':
+      key = { key: providerURL, passphrase: passphrase.toString('base64'), encoding: 'base64' };
+      break;
+    case 'provider-passphrase-buffer': key = { key: providerURL, passphrase }; break;
+    case 'provider-passphrase-arraybuffer':
+      key = { key: providerURL, passphrase: Uint8Array.from(passphrase).buffer };
+      break;
+    case 'provider-direct': key = providerURL; break;
+    default: throw new Error(`Unsupported input: ${input}`);
+  }
+
+  if (input.startsWith('pem-passphrase-')) {
+    const bytes = key.passphrase === undefined ? undefined :
+      typeof key.passphrase === 'string' ? Buffer.from(key.passphrase, key.encoding) :
+        Buffer.from(key.passphrase);
+    key = {
+      key: Buffer.from(privateKey.export({
+        format: 'pem', type: 'pkcs8',
+        ...(bytes === undefined ? {} : { cipher: 'aes-256-cbc', passphrase: bytes }),
+      })),
+      format: 'pem', type: 'pkcs8', passphrase: key.passphrase, encoding: key.encoding,
+    };
+  } else if (key.key instanceof crypto.KeyObject && key.format !== undefined) {
+    const bytes = Buffer.from(key.key.export({ format: key.format, type: key.type }));
+    key.key = key.encoding === undefined ? bytes : bytes.toString(key.encoding);
+  }
+
+  prepareAsymmetricKey(key, ctx);
+  bench.start();
+  for (let index = 0; index < n; index++) {
+    prepareAsymmetricKey(key, ctx);
+  }
+  bench.end(n);
+}
diff --git a/lib/internal/crypto/keys.js b/lib/internal/crypto/keys.js
index 152db0a5f5d1..c935bc1e0d61 100644
--- a/lib/internal/crypto/keys.js
+++ b/lib/internal/crypto/keys.js
@@ -91,6 +91,7 @@ const {
 } = require('internal/util');
 
 const { inspect } = require('internal/util/inspect');
+const { Buffer } = require('buffer');
 
 // Key input contexts.
 const kConsumePublic = 0;
@@ -378,7 +379,7 @@ const {
   return [KeyObject, SecretKeyObject, PublicKeyObject, PrivateKeyObject];
 });
 
-function parseKeyFormat(formatStr, defaultFormat, optionName) {
+function parseKeyFormat(formatStr, defaultFormat, objName) {
   if (formatStr === undefined && defaultFormat !== undefined)
     return defaultFormat;
   else if (formatStr === 'pem')
@@ -393,10 +394,10 @@ function parseKeyFormat(formatStr, defaultFormat, optionName) {
     return kKeyFormatRawPrivate;
   else if (formatStr === 'raw-seed')
     return kKeyFormatRawSeed;
-  throw new ERR_INVALID_ARG_VALUE(optionName, formatStr);
+  throw new ERR_INVALID_ARG_VALUE(option('format', objName), formatStr);
 }
 
-function parseKeyType(typeStr, required, keyType, isPublic, optionName) {
+function parseKeyType(typeStr, required, keyType, isPublic, objName) {
   if (typeStr === undefined && !required) {
     return undefined;
   } else if (typeStr === 'pkcs1') {
@@ -417,7 +418,7 @@ function parseKeyType(typeStr, required, keyType, isPublic, optionName) {
     return kKeyEncodingSEC1;
   }
 
-  throw new ERR_INVALID_ARG_VALUE(optionName, typeStr);
+  throw new ERR_INVALID_ARG_VALUE(option('type', objName), typeStr);
 }
 
 function option(name, prefix) {
@@ -431,7 +432,7 @@ function parseKeyFormatAndType(enc, keyType, isPublic, objName) {
   const isInput = keyType === undefined;
   const format = parseKeyFormat(formatStr,
                                 isInput ? kKeyFormatPEM : undefined,
-                                option('format', objName));
+                                objName);
 
   if (format === kKeyFormatRawPublic) {
     if (isPublic === false) {
@@ -467,7 +468,7 @@ function parseKeyFormatAndType(enc, keyType, isPublic, objName) {
                             isRequired,
                             keyType,
                             isPublic,
-                            option('type', objName));
+                            objName);
   return { format, type };
 }
 
@@ -477,6 +478,10 @@ function isStringOrBuffer(val) {
          isAnyArrayBuffer(val);
 }
 
+function encodeKeyString(value, encoding) {
+  return Buffer.from(value, encoding === 'buffer' ? 'utf8' : encoding);
+}
+
 function parseKeyEncoding(enc, keyType, isPublic, objName) {
   validateObject(enc, 'options');
 
@@ -524,8 +529,8 @@ function parseKeyEncoding(enc, keyType, isPublic, objName) {
     }
   }
 
-  if (passphrase !== undefined)
-    passphrase = getArrayBufferOrView(passphrase, 'key.passphrase', encoding);
+  if (typeof passphrase === 'string')
+    passphrase = encodeKeyString(passphrase, encoding);
 
   return { format, type, cipher, passphrase };
 }
@@ -553,11 +558,11 @@ function validateAsymmetricKeyType(type, ctx, key) {
     );
   }
 
-  if (type !== 'private') {
+  if (type !== kKeyTypePrivate) {
     if (ctx === kConsumePrivate || ctx === kCreatePublic)
-      throw new ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE(type, 'private');
-    if (type !== 'public') {
-      throw new ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE(type,
+      throw new ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE(keyObjectTypeToString(type), 'private');
+    if (type !== kKeyTypePublic) {
+      throw new ERR_CRYPTO_INVALID_KEY_OBJECT_TYPE(keyObjectTypeToString(type),
                                                    'private or public');
     }
   }
@@ -599,10 +604,9 @@ function prepareStorePrivateKey(url, name, passphrase, encoding, properties) {
     if (!isStringOrBuffer(passphrase)) {
       throw new ERR_INVALID_ARG_VALUE(option('passphrase', name), passphrase);
     }
-    passphrase = getArrayBufferOrView(
-      passphrase,
-      option('passphrase', name),
-      encoding);
+    if (typeof passphrase === 'string') {
+      passphrase = encodeKeyString(passphrase, encoding);
+    }
   }
 
   if (properties !== undefined) {
@@ -627,96 +631,113 @@ function prepareStorePrivateKey(url, name, passphrase, encoding, properties) {
 }
 
 function prepareAsymmetricKey(key, ctx, name = 'key') {
+  if (typeof key === 'string') {
+    return { format: kKeyFormatPEM, data: encodeKeyString(key) };
+  }
+  if (isArrayBufferView(key)) {
+    return { format: kKeyFormatPEM, data: key };
+  }
   const isPrivateKeyInput = ctx === kConsumePrivate || ctx === kCreatePrivate;
 
   if (isKeyObject(key)) {
     // Best case: A key object, as simple as that.
-    const type = getKeyObjectType(key);
-    validateAsymmetricKeyType(type, ctx, key);
-    return { data: getKeyObjectHandle(key) };
+    const slots = getKeyObjectSlots(key);
+    validateAsymmetricKeyType(slots[kKeyObjectSlotType], ctx, key);
+    return { data: slots[kKeyObjectSlotHandle] };
   }
   if (isPrivateKeyInput && isURLInstance(key)) {
     // A private key referenced by a URI for an OpenSSL STORE loader.
     return prepareStorePrivateKey(key, name);
   }
-  if (isStringOrBuffer(key)) {
-    // Expect PEM by default, mostly for backward compatibility.
-    return { format: kKeyFormatPEM, data: getArrayBufferOrView(key, name) };
+  if (isAnyArrayBuffer(key)) {
+    return { format: kKeyFormatPEM, data: key };
   }
   if (typeof key === 'object') {
-    const { key: data, encoding, format, properties } = key;
-
-    // The 'key' property can be a KeyObject as well to allow specifying
-    // additional options such as padding along with the key.
-    if (isKeyObject(data)) {
-      const type = getKeyObjectType(data);
-      validateAsymmetricKeyType(type, ctx, data);
-      return { data: getKeyObjectHandle(data) };
-    }
-    if (isPrivateKeyInput && isURLInstance(data)) {
-      // A private key referenced by a URI for an OpenSSL STORE loader, with
-      // an optional passphrase/PIN.
-      return prepareStorePrivateKey(
-        data,
-        name,
-        key.passphrase,
-        encoding,
-        properties);
-    }
-    if (format === 'jwk') {
-      validateObject(data, `${name}.key`);
-      return { data, format: kKeyFormatJWK };
-    } else if (format === 'raw-public' || format === 'raw-private' ||
+    return prepareAsymmetricKeyOptions(key, ctx, name, isPrivateKeyInput);
+  }
+
+  throw new ERR_INVALID_ARG_TYPE(
+    name,
+    getKeyTypes({
+      allowKeyObject: ctx !== kCreatePrivate,
+      allowURL: isPrivateKeyInput,
+    }),
+    key);
+}
+
+function prepareAsymmetricKeyOptions(key, ctx, name, isPrivateKeyInput) {
+  const { key: data, encoding, format, properties } = key;
+  let isData = typeof data === 'string' || isArrayBufferView(data);
+
+  // The 'key' property can be a KeyObject as well to allow specifying
+  // additional options such as padding along with the key.
+  if (!isData && isKeyObject(data)) {
+    const slots = getKeyObjectSlots(data);
+    validateAsymmetricKeyType(slots[kKeyObjectSlotType], ctx, data);
+    return { data: slots[kKeyObjectSlotHandle] };
+  }
+  isData ||= isAnyArrayBuffer(data);
+  if (!isData && isPrivateKeyInput && isURLInstance(data)) {
+    // A private key referenced by a URI for an OpenSSL STORE loader, with
+    // an optional passphrase/PIN.
+    return prepareStorePrivateKey(
+      data,
+      name,
+      key.passphrase,
+      encoding,
+      properties);
+  }
+  if (format === 'jwk') {
+    validateObject(data, `${name}.key`);
+    return { data, format: kKeyFormatJWK };
+  }
+  if (format === 'raw-public' || format === 'raw-private' ||
                format === 'raw-seed') {
-      if ((ctx === kConsumePrivate || ctx === kCreatePrivate) &&
-          format === 'raw-public') {
-        throw new ERR_INVALID_ARG_VALUE(`${name}.format`, format);
-      }
-      if (!isArrayBufferView(data) && !isAnyArrayBuffer(data)) {
-        throw new ERR_INVALID_ARG_TYPE(
-          `${name}.key`,
-          ['ArrayBuffer', 'Buffer', 'TypedArray', 'DataView'],
-          data);
-      }
-      validateString(key.asymmetricKeyType, `${name}.asymmetricKeyType`);
-      if (key.asymmetricKeyType === 'ec') {
-        validateString(key.namedCurve, `${name}.namedCurve`);
-      }
-      const rawFormat = parseKeyFormat(format, undefined, `${name}.format`);
-      return {
-        data: getArrayBufferOrView(data, `${name}.key`),
-        format: rawFormat,
-        type: key.asymmetricKeyType,
-        namedCurve: key.namedCurve ?? null,
-      };
+    if (isPrivateKeyInput && format === 'raw-public') {
+      throw new ERR_INVALID_ARG_VALUE(`${name}.format`, format);
     }
-
-    // Either PEM or DER using PKCS#1 or SPKI.
-    if (!isStringOrBuffer(data)) {
+    if (!isData || typeof data === 'string') {
       throw new ERR_INVALID_ARG_TYPE(
         `${name}.key`,
-        getKeyTypes({
-          allowKeyObject: ctx !== kCreatePrivate,
-          allowURL: isPrivateKeyInput,
-        }),
+        ['ArrayBuffer', 'Buffer', 'TypedArray', 'DataView'],
         data);
     }
-
-    const isPublic =
-      (ctx === kConsumePrivate || ctx === kCreatePrivate) ? false : undefined;
+    validateString(key.asymmetricKeyType, `${name}.asymmetricKeyType`);
+    if (key.asymmetricKeyType === 'ec') {
+      validateString(key.namedCurve, `${name}.namedCurve`);
+    }
+    const rawFormat = format === 'raw-public' ? kKeyFormatRawPublic :
+      format === 'raw-private' ? kKeyFormatRawPrivate : kKeyFormatRawSeed;
     return {
-      data: getArrayBufferOrView(data, `${name}.key`, encoding),
-      ...parseKeyEncoding(key, undefined, isPublic, name),
+      data,
+      format: rawFormat,
+      type: key.asymmetricKeyType,
+      namedCurve: key.namedCurve ?? null,
     };
   }
 
-  throw new ERR_INVALID_ARG_TYPE(
-    name,
-    getKeyTypes({
-      allowKeyObject: ctx !== kCreatePrivate,
-      allowURL: isPrivateKeyInput,
-    }),
-    key);
+  // Either PEM or DER using PKCS#1 or SPKI.
+  if (!isData) {
+    throw new ERR_INVALID_ARG_TYPE(
+      `${name}.key`,
+      getKeyTypes({
+        allowKeyObject: ctx !== kCreatePrivate,
+        allowURL: isPrivateKeyInput,
+      }),
+      data);
+  }
+
+  const isPublic = isPrivateKeyInput ? false : undefined;
+  const keyData = typeof data === 'string' ?
+    encodeKeyString(data, encoding) : data;
+  const parsed = parseKeyEncoding(key, undefined, isPublic, name);
+  return {
+    data: keyData,
+    format: parsed.format,
+    type: parsed.type,
+    cipher: parsed.cipher,
+    passphrase: parsed.passphrase,
+  };
 }
 
 function preparePrivateKey(key, name) {
@@ -1414,6 +1435,11 @@ module.exports = {
   parsePrivateKeyEncoding,
   parseKeyEncoding,
   toPublicCryptoKey,
+  prepareAsymmetricKey,
+  kConsumePublic,
+  kConsumePrivate,
+  kCreatePublic,
+  kCreatePrivate,
   preparePrivateKey,
   preparePublicOrPrivateKey,
   prepareSecretKey,
diff --git a/test/parallel/test-crypto-prepare-asymmetric-key.js b/test/parallel/test-crypto-prepare-asymmetric-key.js
new file mode 100644
index 000000000000..de5ea1b483d1
--- /dev/null
+++ b/test/parallel/test-crypto-prepare-asymmetric-key.js
@@ -0,0 +1,101 @@
+'use strict';
+
+// Flags: --expose-internals
+
+const common = require('../common');
+if (!common.hasCrypto) common.skip('missing crypto');
+const assert = require('node:assert');
+const crypto = require('node:crypto');
+const fixtures = require('../common/fixtures');
+const {
+  prepareAsymmetricKey,
+  getKeyObjectHandle,
+  kConsumePublic,
+  kConsumePrivate,
+  kCreatePublic,
+  kCreatePrivate,
+} = require('internal/crypto/keys');
+
+const pem = fixtures.readKey('ec_p256_private.pem');
+const keyObject = crypto.createPrivateKey(pem);
+const contexts = [kConsumePublic, kConsumePrivate, kCreatePublic, kCreatePrivate];
+
+for (const input of [
+  pem,
+  new Uint8Array(pem),
+  new DataView(Uint8Array.from(pem).buffer),
+  Uint8Array.from(pem).buffer,
+  new SharedArrayBuffer(pem.length),
+]) {
+  Object.defineProperty(input, 'key', { get: common.mustNotCall() });
+  Object.defineProperty(input, 'format', { get: common.mustNotCall() });
+  Object.defineProperty(input, Symbol.toStringTag, { value: 'KeyObject' });
+  for (const context of contexts) {
+    assert.strictEqual(prepareAsymmetricKey(input, context).data, input);
+    assert.strictEqual(prepareAsymmetricKey({ key: input }, context).data, input);
+  }
+}
+
+for (const context of [kConsumePublic, kConsumePrivate, kCreatePublic]) {
+  const options = { key: keyObject, format: 'raw-public', asymmetricKeyType: 'invalid' };
+  assert.strictEqual(prepareAsymmetricKey(options, context).data, getKeyObjectHandle(keyObject));
+}
+
+{
+  const reads = [];
+  const values = { key: pem.toString(), encoding: 'utf8', format: 'pem' };
+  const options = {};
+  for (const name of ['key', 'encoding', 'format', 'properties', 'type', 'cipher', 'passphrase']) {
+    Object.defineProperty(options, name, {
+      get() {
+        reads.push(name);
+        return values[name];
+      },
+    });
+  }
+  assert.deepStrictEqual(prepareAsymmetricKey(options, kConsumePrivate).data, pem);
+  assert.deepStrictEqual(reads, [
+    'key', 'encoding', 'format', 'properties', 'format', 'type', 'cipher', 'passphrase', 'encoding',
+  ]);
+}
+
+{
+  const input = {
+    key: pem.toString(),
+    encoding: 'invalid',
+    get format() { return 'pem'; },
+    get type() { return assert.fail('String conversion must precede encoding option parsing'); },
+  };
+  assert.throws(() => prepareAsymmetricKey(input, kConsumePrivate), { code: 'ERR_UNKNOWN_ENCODING' });
+}
+
+{
+  const raw = keyObject.export({ format: 'raw-private' });
+  const input = { key: raw, format: 'raw-private', asymmetricKeyType: 'ec', namedCurve: 'P-256' };
+  assert.strictEqual(prepareAsymmetricKey(input, kConsumePrivate).data, raw);
+  assert.throws(() => prepareAsymmetricKey({ ...input, key: raw.toString('hex') }, kConsumePrivate), {
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+}
+
+for (const encoding of [undefined, 'buffer', 'utf8', 'hex', 'base64']) {
+  const inputEncoding = encoding === 'buffer' ? 'utf8' : encoding;
+  const passphrase = Buffer.from('password');
+  const result = prepareAsymmetricKey({
+    key: pem.toString(inputEncoding),
+    passphrase: passphrase.toString(inputEncoding),
+    encoding,
+  }, kConsumePrivate);
+  assert.deepStrictEqual(result.data, pem);
+  assert.deepStrictEqual(result.passphrase, passphrase);
+}
+
+for (const [options, optionName] of [
+  [{ format: 'invalid' }, 'format'],
+  [{ format: 'der', type: 'invalid' }, 'type'],
+]) {
+  assert.throws(() => prepareAsymmetricKey({ key: pem, ...options }, kConsumePrivate, 'options.key'), {
+    code: 'ERR_INVALID_ARG_VALUE',
+    message: new RegExp(`options\\.key\\.${optionName}`),
+  });
+}