ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
XML signature validation in AIR
By obtaining, directly from the signer, a copy of the certificate, another certificate that serves as a trust anchor
for the certificate, or sufficient information to reliably identify the certificate, such as the public key.
Asking the end user of your application if they trust the certificate. Such a query is invalid with self-signed
certificates since the identifying information in the certificate is inherently unreliable.
The runtime verifies the cryptographic integrity of the signed data.
The signed data is verified with the help of your IURIDereferencer implementation. For each reference in the
signature document, the IURIDereferencer implementation dereference() method is called. The data returned
by the dereference() method is used to compute the reference digest. This digest value is compared to the digest
recorded in the signature document. If the digests match, then the data has not been altered since it was signed.
One important consideration when relying on the results of validating an XML signature is that only what is signed
is secure. For example, consider a signed manifest listing the files in a package. When the XMLSignatureValidator
verifies the signature, it only checks whether the manifest itself is unaltered. The data in the files is not signed, so
the signature will still validate when files referenced in the manifest are changed or deleted.
Note: To verify files in such a manifest, you can compute the digest of the file data (using the same hashing algorithm
used in the manifest) and compare the result to the digest stored in the signed manifest. In some cases, you should also
check for the presence of additional files.
Interpreting validation results
Adobe AIR 1.5 and later
The validation results are reported by the status properties of the XMLSignatureValidator object. These properties can
be read after the validator object dispatches the complete event. The four status properties include: validityStatus,
digestStatus, identityStatus, and referencesStatus.
The validityStatus property
Adobe AIR 1.5 and later
The validityStatus property reports the overall validity of the signature. The validityStatus depends on the state
of the other three status properties and can have one of the following values:
valid — If digestStatus, identityStatus, and referencesStatus are all valid.
invalid — If one or more of the individual status properties is invalid.
unknown — If one or more of the individual status properties is unknown and no individual status is invalid.
The digestStatus property
Adobe AIR 1.5 and later
The digestStatus property reports the results of the cryptographic verification of the message digest. The
digestStatus property can have one of the following values:
valid — If the signature document itself is unaltered since signing.
invalid — If the signature document has been altered or is malformed.
unknown — If the verify() method has not completed without error.
Last updated 6/6/2012
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