the Chromium logo

The Chromium Projects
Blink (Rendering Engine) >

WebCrypto

Accessing it

Standards compliance

Chromium's implementation follows the Web Cryptography API Editor's Draft.

Be sure to refer to the copy of the spec on github NOT the one hosted on w3c.org.

The version on w3c.org is horribly out of date (as of October 3 2016).

Reporting bugs

Supported algorithms (as of Chrome 53)

The WebCrypto specification does not mandate any particular algorithms.

At this time Chromium implements all of the algorithms described by the main specification:

Algorithm Supported Notes
RSASSA-PKCS1-v1_5 YES
RSA-PSS YES
RSA-OAEP YES
ECDSA YES
ECDH YES
AES-CTR YES
AES-CBC YES
AES-GCM YES
AES-KW YES
HMAC YES
SHA-1 YES
SHA-256 YES
SHA-384 YES
SHA-512 YES
HKDF YES
PBKDF2 YES

Abandoned algorithms

Earlier drafts of the specification contained additional algorithms, which have since been pulled from both the spec and from Chromium's implementation:

    • Algorithm Supported Notes
    AES-CMAC NO No longer part of the spec Was never implemented by Chrome
    AES-CFB NO No longer part of the spec Was never implemented by Chrome
    Diffie-Hellman NO No longer part of the spec Was never implemented by Chrome
    Concat KDF NO No longer part of the spec Was never implemented by Chrome
    HKDF-CTR NO No longer part of the spec Was never implemented by Chrome The spec has redefined this as 
              href="https://github.com/w3c/webcrypto/issues/27">redefined this
          as HKDF</a></td>
    RSAES-PKCS1-v1_5 NO No longer part of the spec. Chrome supported this in early days before Web Crypto was 
              enabled by default, but has since dropped support.</td>

    RSA support

    *   The modulus length must be a multiple of 8 bits
*   The modulus length must be &gt;= 256 and &lt;= 16384 bits
*   When *generating* RSA keys the public exponent must be 3 or
            65537. This limitation does not apply when importing keys.

    AES support

    *   The supported key sizes are:
    *   128 bits
    *   256 bits
    *   192 bit AES keys are not supported

    EC support

    *   The supported
            [namedCurves](https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#dfn-NamedCurve)
            are:
    *   P-256
    *   P-384
    *   P-521

    Supported key formats

    Chromium's WebCrypto implementation supports all of the key formats - "raw", "spki", "pkcs8", "jwk", with the following caveats:

    Examples of how to use WebCrypto

    Some examples of using WebCrypto can be found in the Blink LayoutTests.

    (These can't be run directly in the browser because they access functionality from the test harness, however it gives an idea of how to call the various operations)

    Usage data for WebCrypto

    Google Chrome measures how commonly WebCrypto algorithms and methods are across web pages. To explore the data use the Chromium feature stack rank dashboard. This counts the number of pageloads that made use of the given feature (internal users can navigate an equivalent histogram using "WebCore.FeatureObserver"). For details on how the metrics are measured read the comment block in CryptoHistograms.h. Here is the correspondence between the feature names found on the Chromium feature stack rank dashboard and WebCrypto's operations/algorithms:

    Feature WebCrypto method
    `CryptoGetRandomValues` crypto.getRandomValues()
    `SubtleCryptoEncrypt` crypto.subtle.encrypt()
    `SubtleCryptoDecrypt` crypto.subtle.decrypt()
    `SubtleCryptoSign` crypto.subtle.sign()
    `SubtleCryptoVerify` crypto.subtle.verify()
    `SubtleCryptoDigest` crypto.subtle.digest()
    `SubtleCryptoGenerateKey` crypto.subtle.generateKey()
    `SubtleCryptoImportKey` crypto.subtle.importKey()
    `SubtleCryptoExportKey` crypto.subtle.exportKey()
    `SubtleCryptoDeriveBits` crypto.subtle.deriveBits()
    `SubtleCryptoDeriveKey` crypto.subtle.deriveKey()
    `SubtleCryptoWrapKey` crypto.subtle.wrapKey()
    `SubtleCryptoUnwrapKey` crypto.subtle.unwrapKey()
    Feature WebCrypto algorithm
    CryptoAlgorithmAesCbc ` AES-CBC
    `CryptoAlgorithmHmac` HMAC
    `CryptoAlgorithmRsaSsaPkcs1v1_5` RSASSA-PKCS1-v1_5
    `CryptoAlgorithmSha1` SHA-1
    `CryptoAlgorithmSha256` SHA-256
    `CryptoAlgorithmSha384` SHA-384
    `CryptoAlgorithmSha512` SHA-512
    `CryptoAlgorithmAesGcm` AES-GCM
    `CryptoAlgorithmRsaOaep` RSA-OAEP
    `CryptoAlgorithmAesCtr` AES-CTR
    `CryptoAlgorithmAesKw` AES-KW
    `CryptoAlgorithmRsaPss` RSA-PSS
    `CryptoAlgorithmEcdsa` ECDSA
    `CryptoAlgorithmEcdh` ECDH
    `CryptoAlgorithmHkdf` HKDF
    `CryptoAlgorithmPbkdf2` PBKDF2

    Chromium developer's guide

    This section is intended for Chromium developers writing patches to address WebCrypto bugs/features.

    Code location reference

    Running the Chromium unit-tests

    cd src

    ninja -C out/Debug components_unittests

    ./out/Debug/components_unittests --gtest_filter="WebCrypto*"

    cd src/third_party/WebKit

    ./Tools/Scripts/run-webkit-tests --debug crypto

    Getting "XOpenDisplay failed" when running unittests

    Unfortunately components_unittests requires a display to run, even though WebCrypto itself has no such dependency. If you are running from a terminal and get this error the easiest fix is to use Xvfb to create a mock display server (on port 4 in my example)

    #Run this in the background.... Xvfb :4 -screen 0 1024x768x24

    And once it is up, re-run the unit-tests with its display port

    DISPLAY:4 ./out/Debug/components_unittests --gtest_filter="WebCrypto*"