C2PAVerifier Class

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Extracts and validates the C2PA Manifests embedded in an asset.

Syntax

class ipworksllm.C2PAVerifier

Remarks

The C2PAVerifier class reads the Content Credentials embedded in an asset and reports what can be established about them: whether the signature is intact, whether the signer is trusted, and whether the asset bytes still match what was signed.

Supported Formats

JPEG, PNG and PDF are supported. The format is detected from the asset itself, and an asset in any other format is refused rather than reported as carrying no provenance, since those are different answers.

The PDF reader locates the manifest by its file specification's AFRelationship, so it reads manifests written by any conforming tool, not only those this product produced.

Validating an Asset

Set input_file to the asset and call verify. Every manifest found is then added to the manifests properties, and one entry per check performed is added to validation_results.

C2PAVerifier verifier = new C2PAVerifier(); verifier.InputFile = "photo-signed.jpg"; verifier.Verify(); foreach (C2PAValidationResult result in verifier.ValidationResults) Console.WriteLine(result.Severity + " " + result.Code + ": " + result.Explanation);

Reading the Results

Validation is not a single boolean. The C2PA specification defines a status code for each individual check, and the class reports them verbatim so an application can decide how much weight to give each one. A signature that verifies but whose signer is not on a trust list is a different situation from one whose content binding fails.

Each entry in validation_results carries a Severity of success, informational, or failure. Codes such as claimSignature.validated and assertion.dataHash.match are successes; assertion.dataHash.mismatch means the asset was altered after signing; signingCredential.untrusted means the signature is intact but the signer does not chain to any configured trust anchor.

The on_validation_status event fires once for each result as it is produced, which is convenient when validation should be reported incrementally rather than inspected afterwards.

The Provenance Chain

An asset may carry more than one manifest: the active manifest describes the most recent edit, and earlier manifests describe the ingredients it was built from. All of them appear in manifests, with active_manifest_index identifying the active one.

verifier.Verify(); C2PAManifest active = verifier.Manifests[verifier.ActiveManifestIndex]; Console.WriteLine("Produced by " + active.ClaimGenerator + ", signed by " + active.SignerSubject);

Trust Anchors

By default the class validates signing certificates against the built-in C2PA trust list. Additional anchors are supplied through the trusted_certs properties, and are used in addition to the built-in list rather than instead of it, as the C2PA specification prescribes. Setting use_c2_pa_trust_list to False restricts validation to the supplied anchors alone, which is the correct configuration for a private PKI.

Setting check_revocation to True additionally performs online revocation checking. Revocation information stapled into the manifest by the signer is always used when present, whether or not online checking is enabled.

Property List

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The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the class with short descriptions. Click on the links for further details.

active_manifest_index property

The index of the active manifest in the Manifests collection.

Syntax

def get_active_manifest_index() -> int: ...


active_manifest_index = property(get_active_manifest_index, None)

Default Value

-1

Remarks

This property identifies which item in manifests is the active manifest, the one describing how the asset reached its current state. The C2PA specification fixes the active manifest as the last one in the manifest store.

The value is -1 when no manifest was found.

This property is read-only.

check_revocation property

Whether online revocation checking is performed.

Syntax

def get_check_revocation() -> bool: ...

def set_check_revocation(value: bool) -> None: ...


check_revocation = property(get_check_revocation, set_check_revocation)

Default Value

False

Remarks

This property controls whether the class contacts OCSP responders or downloads CRLs to determine whether the signing certificate has been revoked.

Revocation information stapled into the manifest by the signer is always used when present, whether or not this property is set. Setting it to True additionally performs an online check, which requires network access and makes verification slower.

When revocation cannot be determined, verification does not fail; an informational result such as signingCredential.ocsp.inaccessible or signingCredential.ocsp.skipped is reported so the application can decide what that is worth.

The default value is False.

ingredient_count property

The number of records in the Ingredient arrays.

Syntax

def get_ingredient_count() -> int: ...

def set_ingredient_count(value: int) -> None: ...


ingredient_count = property(get_ingredient_count, set_ingredient_count)

Default Value

0

Remarks

This property controls the size of the following arrays:

• ingredient_format
• ingredient_instance_id
• ingredient_manifest_label
• ingredient_relationship
• ingredient_title

The array indices start at 0 and end at ingredient_count - 1.

ingredient_format property

The media type of the ingredient asset.

Syntax

def get_ingredient_format(ingredient_index: int) -> str: ...

def set_ingredient_format(ingredient_index: int, value: str) -> None: ...

Default Value

""

Remarks

The media type of the ingredient asset.

This field holds the media type of the asset that went into this one, for example image/jpeg, image/png or application/pdf. The class fills it in from the source asset when the ingredient is added.

The ingredient_index parameter specifies the index of the item in the array. The size of the array is controlled by the ingredient_count property.

ingredient_instance_id property

The instance identifier of the ingredient asset.

Syntax

def get_ingredient_instance_id(ingredient_index: int) -> str: ...

def set_ingredient_instance_id(ingredient_index: int, value: str) -> None: ...

Default Value

""

Remarks

The instance identifier of the ingredient asset.

This field holds the identifier of the exact version of the asset that went into this one, normally an XMP instance identifier such as xmp:iid:....

When the ingredient carried a C2PA Manifest of its own, the class fills this in from that Manifest's claim, so the reference names the precise version that was used rather than the document in general.

Version 2 of the ingredient assertion also carried a document identifier. Version 3, which this class writes, removed it, so there is no corresponding field.

The ingredient_index parameter specifies the index of the item in the array. The size of the array is controlled by the ingredient_count property.

ingredient_manifest_label property

The label of the ingredient's own C2PA Manifest.

Syntax

def get_ingredient_manifest_label(ingredient_index: int) -> str: ...

def set_ingredient_manifest_label(ingredient_index: int, value: str) -> None: ...

Default Value

""

Remarks

The label of the ingredient's own C2PA Manifest.

This field identifies the manifest that describes the ingredient, when the ingredient carried one. It is the urn:c2pa label of that manifest within the same manifest store.

An empty value means the ingredient arrived without provenance data of its own.

The ingredient_index parameter specifies the index of the item in the array. The size of the array is controlled by the ingredient_count property.

ingredient_relationship property

How the ingredient relates to the asset.

Syntax

def get_ingredient_relationship(ingredient_index: int) -> str: ...

def set_ingredient_relationship(ingredient_index: int, value: str) -> None: ...

Default Value

"componentOf"

Remarks

How the ingredient relates to the asset.

This field describes the ingredient's role. The C2PA specification defines the following values:

The default value is componentOf.

The ingredient_index parameter specifies the index of the item in the array. The size of the array is controlled by the ingredient_count property.

ingredient_title property

A human-readable name for the ingredient.

Syntax

def get_ingredient_title(ingredient_index: int) -> str: ...

def set_ingredient_title(ingredient_index: int, value: str) -> None: ...

Default Value

""

Remarks

A human-readable name for the ingredient.

This field holds a title for the ingredient asset, typically its filename, so a consumer can present the provenance chain in terms a person recognises.

The ingredient_index parameter specifies the index of the item in the array. The size of the array is controlled by the ingredient_count property.

input_data property

The asset to process, held in memory.

Syntax

def get_input_data() -> bytes: ...

def set_input_data(value: bytes) -> None: ...


input_data = property(get_input_data, set_input_data)

Default Value

""

Remarks

This property specifies the asset to be processed as a byte array, for applications that do not work with files on disk.

When both input_file and this property are set, input_file takes precedence.

input_file property

The asset to process.

Syntax

def get_input_file() -> str: ...

def set_input_file(value: str) -> None: ...


input_file = property(get_input_file, set_input_file)

Default Value

""

Remarks

This property specifies the asset to be processed. Set it to the full or relative path of the file.

When both this property and input_data are set, this property takes precedence.

manifest_count property

The number of records in the Manifest arrays.

Syntax

def get_manifest_count() -> int: ...


manifest_count = property(get_manifest_count, None)

Default Value

0

Remarks

This property controls the size of the following arrays:

• manifest_claim_generator
• manifest_is_active
• manifest_label
• manifest_signer_subject
• manifest_signing_time

The array indices start at 0 and end at manifest_count - 1.

This property is read-only.

manifest_claim_generator property

The tool that produced this manifest.

Syntax

def get_manifest_claim_generator(manifest_index: int) -> str: ...

Default Value

""

Remarks

The tool that produced this manifest.

This field names the application that created the claim, as recorded by its signer.

It is a claim, not a verified fact: it says what the signer wrote down. What the signature establishes is who wrote it, which is manifest_signer_subject.

The manifest_index parameter specifies the index of the item in the array. The size of the array is controlled by the manifest_count property.

This property is read-only.

manifest_is_active property

Whether this is the active manifest.

Syntax

def get_manifest_is_active(manifest_index: int) -> bool: ...

Default Value

False

Remarks

Whether this is the active manifest.

This field is True for the manifest that describes how the asset reached its current state, and False for the manifests that came with its ingredients.

The C2PA specification fixes the active manifest as the last one in the manifest store.

The manifest_index parameter specifies the index of the item in the array. The size of the array is controlled by the manifest_count property.

This property is read-only.

manifest_label property

The manifest's identifier.

Syntax

def get_manifest_label(manifest_index: int) -> str: ...

Default Value

""

Remarks

The manifest's identifier.

This field holds the manifest's label, a urn:c2pa value that uniquely identifies it within the manifest store. Ingredients refer to their manifests by this value.

The manifest_index parameter specifies the index of the item in the array. The size of the array is controlled by the manifest_count property.

This property is read-only.

manifest_signer_subject property

The subject of the certificate that signed the claim.

Syntax

def get_manifest_signer_subject(manifest_index: int) -> str: ...

Default Value

""

Remarks

The subject of the certificate that signed the claim.

This field holds the distinguished name of the signing certificate's subject.

This is the identity the signature actually establishes, provided the certificate chains to a trust anchor. Check the validation results for signingCredential.trusted before treating it as meaningful: an untrusted certificate can carry any subject its issuer chose to put in it.

The manifest_index parameter specifies the index of the item in the array. The size of the array is controlled by the manifest_count property.

This property is read-only.

manifest_signing_time property

When the claim was signed.

Syntax

def get_manifest_signing_time(manifest_index: int) -> str: ...

Default Value

""

Remarks

When the claim was signed.

This field holds the signing time as an RFC 3339 date and time.

When the manifest carries an RFC 3161 time-stamp, this is the time attested by the Time Stamping Authority, and it is what allows the signature to remain verifiable after the signing certificate expires. Without a time-stamp the value is the signer's own claimed time, which carries no more weight than the rest of the claim.

The manifest_index parameter specifies the index of the item in the array. The size of the array is controlled by the manifest_count property.

This property is read-only.

trusted_cert_count property

The number of records in the TrustedCert arrays.

Syntax

def get_trusted_cert_count() -> int: ...

def set_trusted_cert_count(value: int) -> None: ...


trusted_cert_count = property(get_trusted_cert_count, set_trusted_cert_count)

Default Value

0

Remarks

This property controls the size of the following arrays:

• trusted_cert_effective_date
• trusted_cert_encoded
• trusted_cert_expiration_date
• trusted_cert_extended_key_usage
• trusted_cert_fingerprint
• trusted_cert_fingerprint_sha1
• trusted_cert_fingerprint_sha256
• trusted_cert_issuer
• trusted_cert_private_key
• trusted_cert_private_key_available
• trusted_cert_private_key_container
• trusted_cert_public_key
• trusted_cert_public_key_algorithm
• trusted_cert_public_key_length
• trusted_cert_serial_number
• trusted_cert_signature_algorithm
• trusted_cert_store
• trusted_cert_store_password
• trusted_cert_store_type
• trusted_cert_subject
• trusted_cert_subject_alt_names
• trusted_cert_thumbprint_md5
• trusted_cert_thumbprint_sha1
• trusted_cert_thumbprint_sha256
• trusted_cert_usage
• trusted_cert_usage_flags
• trusted_cert_version

The array indices start at 0 and end at trusted_cert_count - 1.

trusted_cert_effective_date property

The date on which this certificate becomes valid.

Syntax

def get_trusted_cert_effective_date(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The date on which this certificate becomes valid. Before this date, it is not valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2000 15:00:00.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_encoded property

The certificate (PEM/Base64 encoded).

Syntax

def get_trusted_cert_encoded(trusted_cert_index: int) -> bytes: ...

def set_trusted_cert_encoded(trusted_cert_index: int, value: bytes) -> None: ...

Default Value

""

Remarks

The certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The trusted_cert_store and trusted_cert_subject properties also may be used to specify a certificate.

When trusted_cert_encoded is set, a search is initiated in the current trusted_cert_store for the private key of the certificate. If the key is found, trusted_cert_subject is updated to reflect the full subject of the selected certificate; otherwise, trusted_cert_subject is set to an empty string.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

trusted_cert_expiration_date property

The date on which the certificate expires.

Syntax

def get_trusted_cert_expiration_date(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The date on which the certificate expires. After this date, the certificate will no longer be valid. The date is localized to the system's time zone. The following example illustrates the format of an encoded date:

23-Jan-2001 15:00:00.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_extended_key_usage property

A comma-delimited list of extended key usage identifiers.

Syntax

def get_trusted_cert_extended_key_usage(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

A comma-delimited list of extended key usage identifiers. These are the same as ASN.1 object identifiers (OIDs).

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_fingerprint property

The hex-encoded, 16-byte MD5 fingerprint of the certificate.

Syntax

def get_trusted_cert_fingerprint(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The hex-encoded, 16-byte MD5 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: bc:2a:72:af:fe:58:17:43:7a:5f:ba:5a:7c:90:f7:02

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_fingerprint_sha1 property

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate.

Syntax

def get_trusted_cert_fingerprint_sha1(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The hex-encoded, 20-byte SHA-1 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: 30:7b:fa:38:65:83:ff:da:b4:4e:07:3f:17:b8:a4:ed:80:be:ff:84

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_fingerprint_sha256 property

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate.

Syntax

def get_trusted_cert_fingerprint_sha256(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The hex-encoded, 32-byte SHA-256 fingerprint of the certificate. This property is primarily used for keys which do not have a corresponding X.509 public certificate, such as PEM keys that only contain a private key. It is commonly used for SSH keys.

The following example illustrates the format: 6a:80:5c:33:a9:43:ea:b0:96:12:8a:64:96:30:ef:4a:8a:96:86:ce:f4:c7:be:10:24:8e:2b:60:9e:f3:59:53

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_issuer property

The issuer of the certificate.

Syntax

def get_trusted_cert_issuer(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The issuer of the certificate. This property contains a string representation of the name of the issuing authority for the certificate.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_private_key property

The private key of the certificate (if available).

Syntax

def get_trusted_cert_private_key(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The private key of the certificate (if available). The key is provided as PEM/Base64-encoded data.

NOTE: The trusted_cert_private_key may be available but not exportable. In this case, trusted_cert_private_key returns an empty string.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_private_key_available property

Whether a PrivateKey is available for the selected certificate.

Syntax

def get_trusted_cert_private_key_available(trusted_cert_index: int) -> bool: ...

Default Value

False

Remarks

Whether a trusted_cert_private_key is available for the selected certificate. If trusted_cert_private_key_available is True, the certificate may be used for authentication purposes (e.g., server authentication).

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_private_key_container property

The name of the PrivateKey container for the certificate (if available).

Syntax

def get_trusted_cert_private_key_container(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The name of the trusted_cert_private_key container for the certificate (if available). This functionality is available only on Windows platforms.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_public_key property

The public key of the certificate.

Syntax

def get_trusted_cert_public_key(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The public key of the certificate. The key is provided as PEM/Base64-encoded data.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_public_key_algorithm property

The textual description of the certificate's public key algorithm.

Syntax

def get_trusted_cert_public_key_algorithm(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The textual description of the certificate's public key algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_DH") or an object identifier (OID) string representing the algorithm.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_public_key_length property

The length of the certificate's public key (in bits).

Syntax

def get_trusted_cert_public_key_length(trusted_cert_index: int) -> int: ...

Default Value

0

Remarks

The length of the certificate's public key (in bits). Common values are 512, 1024, and 2048.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_serial_number property

The serial number of the certificate encoded as a string.

Syntax

def get_trusted_cert_serial_number(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The serial number of the certificate encoded as a string. The number is encoded as a series of hexadecimal digits, with each pair representing a byte of the serial number.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_signature_algorithm property

The text description of the certificate's signature algorithm.

Syntax

def get_trusted_cert_signature_algorithm(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The text description of the certificate's signature algorithm. The property contains either the name of the algorithm (e.g., "RSA" or "RSA_MD5RSA") or an object identifier (OID) string representing the algorithm.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_store property

The name of the certificate store for the client certificate.

Syntax

def get_trusted_cert_store(trusted_cert_index: int) -> bytes: ...

def set_trusted_cert_store(trusted_cert_index: int, value: bytes) -> None: ...

Default Value

"MY"

Remarks

The name of the certificate store for the client certificate.

The trusted_cert_store_type property denotes the type of the certificate store specified by trusted_cert_store. If the store is password-protected, specify the password in trusted_cert_store_password.

trusted_cert_store is used in conjunction with the trusted_cert_subject property to specify client certificates. If trusted_cert_store has a value, and trusted_cert_subject or trusted_cert_encoded is set, a search for a certificate is initiated. Please see the trusted_cert_subject property for details.

Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

When the certificate store type is cstPFXFile, this property must be set to the name of the file. When the type is cstPFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

trusted_cert_store_password property

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

Syntax

def get_trusted_cert_store_password(trusted_cert_index: int) -> str: ...

def set_trusted_cert_store_password(trusted_cert_index: int, value: str) -> None: ...

Default Value

""

Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

trusted_cert_store_type property

The type of certificate store for this certificate.

Syntax

def get_trusted_cert_store_type(trusted_cert_index: int) -> int: ...

def set_trusted_cert_store_type(trusted_cert_index: int, value: int) -> None: ...

Possible Values

0 # User
1 # Machine
2 # PFXFile
3 # PFXBlob
4 # JKSFile
5 # JKSBlob
6 # PEMKeyFile
7 # PEMKeyBlob
8 # PublicKeyFile
9 # PublicKeyBlob
10 # SSHPublicKeyBlob
11 # P7BFile
12 # P7BBlob
13 # SSHPublicKeyFile
14 # PPKFile
15 # PPKBlob
16 # XMLFile
17 # XMLBlob
18 # JWKFile
19 # JWKBlob
20 # SecurityKey
21 # BCFKSFile
22 # BCFKSBlob
23 # PKCS11
99 # Auto

Default Value

0

Remarks

The type of certificate store for this certificate.

The class supports both public and private keys in a variety of formats. When the cstAuto value is used, the class will automatically determine the type. This property can take one of the following values:

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

trusted_cert_subject property

The subject of the certificate used for client authentication.

Syntax

def get_trusted_cert_subject(trusted_cert_index: int) -> str: ...

def set_trusted_cert_subject(trusted_cert_index: int, value: str) -> None: ...

Default Value

""

Remarks

The subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=example@email.com". Common fields and their meanings are as follows:

If a field value contains a comma, it must be quoted.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

trusted_cert_subject_alt_names property

Comma-separated lists of alternative subject names for the certificate.

Syntax

def get_trusted_cert_subject_alt_names(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

Comma-separated lists of alternative subject names for the certificate.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_thumbprint_md5 property

The MD5 hash of the certificate.

Syntax

def get_trusted_cert_thumbprint_md5(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The MD5 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_thumbprint_sha1 property

The SHA-1 hash of the certificate.

Syntax

def get_trusted_cert_thumbprint_sha1(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The SHA-1 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_thumbprint_sha256 property

The SHA-256 hash of the certificate.

Syntax

def get_trusted_cert_thumbprint_sha256(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The SHA-256 hash of the certificate. It is primarily used for X.509 certificates. If the hash does not already exist, it is automatically computed.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_usage property

The text description of UsageFlags .

Syntax

def get_trusted_cert_usage(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The text description of trusted_cert_usage_flags.

This value will be one or more of the following strings and will be separated by commas:

• Digital Signature
• Non-Repudiation
• Key Encipherment
• Data Encipherment
• Key Agreement
• Certificate Signing
• CRL Signing
• Encipher Only

If the provider is OpenSSL, the value is a comma-separated list of X.509 certificate extension names.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_usage_flags property

The flags that show intended use for the certificate.

Syntax

def get_trusted_cert_usage_flags(trusted_cert_index: int) -> int: ...

Default Value

0

Remarks

The flags that show intended use for the certificate. The value of trusted_cert_usage_flags is a combination of the following flags:

Please see the trusted_cert_usage property for a text representation of trusted_cert_usage_flags.

This functionality currently is not available when the provider is OpenSSL.

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

trusted_cert_version property

The certificate's version number.

Syntax

def get_trusted_cert_version(trusted_cert_index: int) -> str: ...

Default Value

""

Remarks

The certificate's version number. The possible values are the strings "V1", "V2", and "V3".

The trusted_cert_index parameter specifies the index of the item in the array. The size of the array is controlled by the trusted_cert_count property.

This property is read-only.

use_c2_pa_trust_list property

Whether the built-in C2PA trust list is used.

Syntax

def get_use_c2_pa_trust_list() -> bool: ...

def set_use_c2_pa_trust_list(value: bool) -> None: ...


use_c2_pa_trust_list = property(get_use_c2_pa_trust_list, set_use_c2_pa_trust_list)

Default Value

True

Remarks

This property controls whether signing certificates are validated against the C2PA trust list built into the class, in addition to any anchors in trusted_certs.

The default value is True, which is the configuration the C2PA specification describes for a validator: the trust anchors for the claim signing extended key usage include the C2PA trust list, and a user may configure further anchors on top of it.

Set this property to False to validate against trusted_certs alone, which is appropriate for a private PKI where the public list has no bearing.

The built-in list is a snapshot taken when the class was built. Query the TrustListVersion and TrustListDate configuration settings to determine how current that snapshot is; supply newer anchors through trusted_certs when it has aged.

validation_result_count property

The number of records in the ValidationResult arrays.

Syntax

def get_validation_result_count() -> int: ...


validation_result_count = property(get_validation_result_count, None)

Default Value

0

Remarks

This property controls the size of the following arrays:

• validation_result_code
• validation_result_explanation
• validation_result_manifest_label
• validation_result_severity

The array indices start at 0 and end at validation_result_count - 1.

This property is read-only.

validation_result_code property

The C2PA status code.

Syntax

def get_validation_result_code(validation_result_index: int) -> str: ...

Default Value

""

Remarks

The C2PA status code.

This field holds the status code defined by the C2PA specification, reported verbatim so it can be matched against the specification or passed to another conforming implementation.

Frequently encountered values are:

The validation_result_index parameter specifies the index of the item in the array. The size of the array is controlled by the validation_result_count property.

This property is read-only.

validation_result_explanation property

A human-readable description of the result.

Syntax

def get_validation_result_explanation(validation_result_index: int) -> str: ...

Default Value

""

Remarks

A human-readable description of the result.

This field describes what was checked and what was found, in text suitable for showing to a person or writing to a log.

Application logic should branch on validation_result_code rather than on this text, which is not part of the C2PA specification and may be reworded.

The validation_result_index parameter specifies the index of the item in the array. The size of the array is controlled by the validation_result_count property.

This property is read-only.

validation_result_manifest_label property

The manifest the result applies to.

Syntax

def get_validation_result_manifest_label(validation_result_index: int) -> str: ...

Default Value

""

Remarks

The manifest the result applies to.

This field holds the urn:c2pa label of the manifest that was being checked, so results can be attributed correctly when an asset carries a chain of them.

The validation_result_index parameter specifies the index of the item in the array. The size of the array is controlled by the validation_result_count property.

This property is read-only.

validation_result_severity property

How serious the result is.

Syntax

def get_validation_result_severity(validation_result_index: int) -> int: ...

Default Value

0

Remarks

How serious the result is.

This field classifies the result:

An asset should be treated as validated only when no result carries a severity of 2 and the successes cover the checks the application requires.

The validation_result_index parameter specifies the index of the item in the array. The size of the array is controlled by the validation_result_count property.

This property is read-only.

config method

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

Remarks

config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

reset method

This method will reset the class.

Syntax

def reset() -> None: ...

Remarks

This method will reset the class's properties to their default values.

verify method

Extracts and validates the C2PA Manifests in the asset.

Syntax

def verify() -> None: ...

Remarks

This method reads the asset named by input_file (or held in input_data), locates the C2PA Manifest Store, and validates it. manifests and validation_results are populated when it returns.

For the active manifest, the class verifies the claim signature, builds a certificate path from the signing certificate to the active trust anchors, and recomputes the content binding hash over the asset to confirm the bytes still match what was signed.

C2PAVerifier verifier = new C2PAVerifier(); verifier.InputFile = "photo-signed.jpg"; verifier.Verify(); foreach (C2PAValidationResult result in verifier.ValidationResults) Console.WriteLine(result.Severity + " " + result.Code + ": " + result.Explanation);

A failed check does not throw. It is reported through validation_results and the on_validation_status event, so that a partially trustworthy asset can be described accurately rather than merely rejected. An error is thrown only when the asset cannot be read at all, or carries no C2PA Manifest.

on_error event

Fired when information is available about errors during data delivery.

Syntax

class C2PAVerifierErrorEventParams(object):
  @property
  def error_code() -> int: ...
  @property
  def description() -> str: ...
# In class C2PAVerifier:
@property
def on_error() -> Callable[[C2PAVerifierErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[C2PAVerifierErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

The error_code parameter contains an error code, and the description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

on_log event

This event fires once for each log message.

Syntax

class C2PAVerifierLogEventParams(object):
  @property
  def log_level() -> int: ...
  @property
  def message() -> str: ...
  @property
  def log_type() -> str: ...
# In class C2PAVerifier:
@property
def on_log() -> Callable[[C2PAVerifierLogEventParams], None]: ...
@on_log.setter
def on_log(event_hook: Callable[[C2PAVerifierLogEventParams], None]) -> None: ...

Remarks

This event fires once for each log message generated by the class. The verbosity is controlled by the LogLevel setting.

log_level indicates the level of message. Possible values are as follows:

message is the log entry.

log_type identifies the type of log entry. Possible values are Info, Manifest, Signature, and Validation.

on_manifest_found event

Fires once for each C2PA Manifest found in the asset.

Syntax

class C2PAVerifierManifestFoundEventParams(object):
  @property
  def manifest_label() -> str: ...
  @property
  def claim_generator() -> str: ...
  @property
  def signer_subject() -> str: ...
  @property
  def is_active() -> bool: ...
# In class C2PAVerifier:
@property
def on_manifest_found() -> Callable[[C2PAVerifierManifestFoundEventParams], None]: ...
@on_manifest_found.setter
def on_manifest_found(event_hook: Callable[[C2PAVerifierManifestFoundEventParams], None]) -> None: ...

Remarks

This event fires as each manifest is located, before validation of that manifest completes.

manifest_label is the manifest's identifier, a urn:c2pa value. claim_generator names the tool that produced it. signer_subject is the subject of the certificate that signed the claim. is_active is True for the active manifest, which is the last one in the store.

The same information is available afterwards through the manifests properties; this event is for applications that would rather report provenance as it is discovered.

on_validation_status event

Fires once for each validation status code produced.

Syntax

class C2PAVerifierValidationStatusEventParams(object):
  @property
  def code() -> str: ...
  @property
  def explanation() -> str: ...
  @property
  def severity() -> int: ...
  @property
  def manifest_label() -> str: ...
# In class C2PAVerifier:
@property
def on_validation_status() -> Callable[[C2PAVerifierValidationStatusEventParams], None]: ...
@on_validation_status.setter
def on_validation_status(event_hook: Callable[[C2PAVerifierValidationStatusEventParams], None]) -> None: ...

Remarks

This event fires as each check completes, giving the same information that is appended to validation_results.

code is the status code defined by the C2PA specification, reported verbatim. Common values are claimSignature.validated and assertion.dataHash.match on success, assertion.dataHash.mismatch when the asset was altered after signing, and signingCredential.untrusted when the signature is intact but the signer chains to no configured trust anchor.

explanation is a human-readable description of the check.

severity is 0 (success), 1 (informational), or 2 (failure).

manifest_label identifies which manifest the result applies to.

C2PAVerifier Config Settings

The class accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

C2PAVerifier Config Settings

Base Config Settings

C2PAVerifier Errors

C2PAVerifier Errors