C2PASigner Class

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Creates a C2PA Manifest, signs it, and embeds it into an asset.

Syntax

C2PASigner

Remarks

The C2PASigner class produces Content Credentials: a signed C2PA Manifest that records how an asset was produced, which tool produced it, and whether generative AI was involved. The manifest is embedded directly into the asset, so the provenance travels with the file.

Supported Formats

The class embeds the manifest into the asset itself, so each container format needs its own support. JPEG, PNG and PDF are supported.

The format is detected from the asset itself; there is nothing to configure. An asset in any other format is refused rather than written incorrectly.

For PDF, only documents using classic cross-reference tables can be signed. A document using cross-reference streams is refused, because appending a table-style update to it would produce a file that readers reject.

Signing an Asset

Set InputFile to the asset to be signed, OutputFile to the destination, and SigningCert to a certificate with an associated private key. Calling Sign builds the manifest, signs it, and writes the result.

C2PASigner signer = new C2PASigner(); signer.InputFile = "photo.jpg"; signer.OutputFile = "photo-signed.jpg"; signer.ClaimGenerator = "MyApp/1.0"; signer.SigningCert = new Certificate(CertStoreTypes.cstPFXFile, "signer.pfx", "password", "*"); signer.Sign();

The signing certificate must carry the C2PA claim signing extended key usage, and the manifest is signed with the algorithm named by SignatureAlgorithm. The permitted algorithms are ES256, ES384, ES512, PS256, PS384, PS512, and Ed25519; the C2PA specification permits no others.

Disclosing AI-Generated Content

The most common reason to sign an asset is to disclose how it was created. The AddAction method records a single action in the manifest. Marking an asset as generative AI output is one call.

signer.AddAction("c2pa.created", "http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicMedia", "MyApp/1.0"); signer.Sign();

The second parameter is the digital source type. The C2PA specification requires that a digital source type accompany the c2pa.created action for every asset; use http://c2pa.org/digitalsourcetype/empty when the asset began as a new file with no digital content.

Adding Other Assertions

Anything beyond the assertions the class computes for itself is added with AddAssertion, which appends a raw assertion payload under a given label. This keeps the API stable as the C2PA standard assertion set evolves.

string creativeWork = "{\"@context\":\"https://schema.org\",\"@type\":\"CreativeWork\",\"author\":[{\"@type\":\"Person\",\"name\":\"Jane Doe\"}]}"; signer.AddAssertion("stds.schema-org.CreativeWork", "application/json", System.Text.Encoding.UTF8.GetBytes(creativeWork));

The content binding assertion, which cryptographically ties the manifest to the asset bytes, is always computed by the class and cannot be supplied by the application. Doing so is what makes tampering detectable.

Trusted Time-Stamps

Setting TSAURL to the address of an RFC 3161 Time Stamping Authority adds a trusted time-stamp to the signature. A time-stamped signature remains verifiable after the signing certificate expires, which is why the C2PA specification recommends obtaining one whenever a TSA can be reached.

signer.TSAURL = "http://timestamp.example.com/tsa"; signer.Sign();

Property List

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

Method List

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

Event List

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

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

Actions Property (C2PASigner Class)

The actions recorded in the Manifest.

Syntax

• C++
• C
• Qt

IPWorksLLMList<IPWorksLLMC2PAAction>* GetActions();
int SetActions(IPWorksLLMList<IPWorksLLMC2PAAction>* val);

int ipworksllm_c2pasigner_getactioncount(void* lpObj);
int ipworksllm_c2pasigner_setactioncount(void* lpObj, int iActionCount);

char* ipworksllm_c2pasigner_getaction(void* lpObj, int actionindex);
int ipworksllm_c2pasigner_setaction(void* lpObj, int actionindex, const char* lpszAction);

char* ipworksllm_c2pasigner_getactiondigitalsourcetype(void* lpObj, int actionindex);
int ipworksllm_c2pasigner_setactiondigitalsourcetype(void* lpObj, int actionindex, const char* lpszActionDigitalSourceType);

char* ipworksllm_c2pasigner_getactionsoftwareagent(void* lpObj, int actionindex);
int ipworksllm_c2pasigner_setactionsoftwareagent(void* lpObj, int actionindex, const char* lpszActionSoftwareAgent);

char* ipworksllm_c2pasigner_getactionwhen(void* lpObj, int actionindex);
int ipworksllm_c2pasigner_setactionwhen(void* lpObj, int actionindex, const char* lpszActionWhen);

int getActionCount();
int setActionCount(int iActionCount);

QString getAction(int iActionIndex);
int setAction(int iActionIndex, QString qsAction);

QString getActionDigitalSourceType(int iActionIndex);
int setActionDigitalSourceType(int iActionIndex, QString qsActionDigitalSourceType);

QString getActionSoftwareAgent(int iActionIndex);
int setActionSoftwareAgent(int iActionIndex, QString qsActionSoftwareAgent);

QString getActionWhen(int iActionIndex);
int setActionWhen(int iActionIndex, QString qsActionWhen);

Remarks

Each entry describes something that was done to the content. AddAction is the short way to add one; this collection is how an application reads them back, and how it reaches the When field, which AddAction does not take.

The actions travel in a single c2pa.actions.v2 assertion, written when the Manifest is signed.

Example. Recording when an edit happened:

C2PASigner signer = new C2PASigner(); signer.InputFile = "edited.jpg"; signer.SigningCert = cert; signer.AddAction("c2pa.edited", "", "Acme Editor/3.0"); // AddAction takes no timestamp, so set it on the queued action. signer.Actions[0].When = "2026-09-01T10:30:00Z"; signer.Sign();

Example. Checking what will be recorded before signing:

for (int i = 0; i < signer.Actions.Count; i++) { Console.WriteLine(signer.Actions[i].Action + " by " + signer.Actions[i].SoftwareAgent); }

This property is not available at design time.

Data Type

IPWorksLLMC2PAAction

Assertions Property (C2PASigner Class)

The assertions to record in the C2PA Manifest.

Syntax

• C++
• C
• Qt

IPWorksLLMList<IPWorksLLMC2PAAssertion>* GetAssertions();
int SetAssertions(IPWorksLLMList<IPWorksLLMC2PAAssertion>* val);

int ipworksllm_c2pasigner_getassertioncount(void* lpObj);
int ipworksllm_c2pasigner_setassertioncount(void* lpObj, int iAssertionCount);

char* ipworksllm_c2pasigner_getassertionlabel(void* lpObj, int assertionindex);
int ipworksllm_c2pasigner_setassertionlabel(void* lpObj, int assertionindex, const char* lpszAssertionLabel);

int ipworksllm_c2pasigner_getassertiondata(void* lpObj, int assertionindex, char** lpAssertionData, int* lenAssertionData);
int ipworksllm_c2pasigner_setassertiondata(void* lpObj, int assertionindex, const char* lpAssertionData, int lenAssertionData);

char* ipworksllm_c2pasigner_getassertionmediatype(void* lpObj, int assertionindex);
int ipworksllm_c2pasigner_setassertionmediatype(void* lpObj, int assertionindex, const char* lpszAssertionMediaType);

int getAssertionCount();
int setAssertionCount(int iAssertionCount);

QString getAssertionLabel(int iAssertionIndex);
int setAssertionLabel(int iAssertionIndex, QString qsAssertionLabel);

QByteArray getAssertionData(int iAssertionIndex);
int setAssertionData(int iAssertionIndex, QByteArray qbaAssertionData);

QString getAssertionMediaType(int iAssertionIndex);
int setAssertionMediaType(int iAssertionIndex, QString qsAssertionMediaType);

Remarks

This collection holds the C2PAAssertion items written into the manifest when Sign is called. The AddAssertion and AddAction methods are a convenient way to append items without constructing them directly.

The content binding assertion, which ties the manifest to the asset bytes, is always computed by the class and is not part of this collection. An application cannot supply it, because a self-supplied binding would defeat tamper detection.

This property is not available at design time.

Data Type

IPWorksLLMC2PAAssertion

ClaimGenerator Property (C2PASigner Class)

The identifier of the tool that created the claim.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetClaimGenerator();
int SetClaimGenerator(const char* lpszClaimGenerator);

Unicode (Windows)
LPWSTR GetClaimGenerator();
INT SetClaimGenerator(LPCWSTR lpszClaimGenerator);

char* ipworksllm_c2pasigner_getclaimgenerator(void* lpObj);
int ipworksllm_c2pasigner_setclaimgenerator(void* lpObj, const char* lpszClaimGenerator);

QString getClaimGenerator();
int setClaimGenerator(QString qsClaimGenerator);

Default Value

""

Remarks

This property identifies the application that produced the C2PA Manifest, and is recorded in the claim so a consumer can see which tool made the provenance assertion.

Use a name and version, for example MyApp/1.0. When this property is left empty, the class records its own name and version.

This property is not available at design time.

Data Type

String

Ingredients Property (C2PASigner Class)

The ingredients recorded in the Manifest.

Syntax

• C++
• C
• Qt

IPWorksLLMList<IPWorksLLMC2PAIngredient>* GetIngredients();
int SetIngredients(IPWorksLLMList<IPWorksLLMC2PAIngredient>* val);

int ipworksllm_c2pasigner_getingredientcount(void* lpObj);
int ipworksllm_c2pasigner_setingredientcount(void* lpObj, int iIngredientCount);

char* ipworksllm_c2pasigner_getingredientformat(void* lpObj, int ingredientindex);
int ipworksllm_c2pasigner_setingredientformat(void* lpObj, int ingredientindex, const char* lpszIngredientFormat);

char* ipworksllm_c2pasigner_getingredientinstanceid(void* lpObj, int ingredientindex);
int ipworksllm_c2pasigner_setingredientinstanceid(void* lpObj, int ingredientindex, const char* lpszIngredientInstanceId);

char* ipworksllm_c2pasigner_getingredientmanifestlabel(void* lpObj, int ingredientindex);
int ipworksllm_c2pasigner_setingredientmanifestlabel(void* lpObj, int ingredientindex, const char* lpszIngredientManifestLabel);

char* ipworksllm_c2pasigner_getingredientrelationship(void* lpObj, int ingredientindex);
int ipworksllm_c2pasigner_setingredientrelationship(void* lpObj, int ingredientindex, const char* lpszIngredientRelationship);

char* ipworksllm_c2pasigner_getingredienttitle(void* lpObj, int ingredientindex);
int ipworksllm_c2pasigner_setingredienttitle(void* lpObj, int ingredientindex, const char* lpszIngredientTitle);

int getIngredientCount();
int setIngredientCount(int iIngredientCount);

QString getIngredientFormat(int iIngredientIndex);
int setIngredientFormat(int iIngredientIndex, QString qsIngredientFormat);

QString getIngredientInstanceId(int iIngredientIndex);
int setIngredientInstanceId(int iIngredientIndex, QString qsIngredientInstanceId);

QString getIngredientManifestLabel(int iIngredientIndex);
int setIngredientManifestLabel(int iIngredientIndex, QString qsIngredientManifestLabel);

QString getIngredientRelationship(int iIngredientIndex);
int setIngredientRelationship(int iIngredientIndex, QString qsIngredientRelationship);

QString getIngredientTitle(int iIngredientIndex);
int setIngredientTitle(int iIngredientIndex, QString qsIngredientTitle);

Remarks

Each entry is an asset that went into the one being signed, added by AddIngredient. This collection is how an application reads them back before signing.

When an ingredient's source carried a Manifest of its own, ManifestLabel names it and that Manifest is carried in the store being written. When it did not, ManifestLabel is empty: the ingredient records what the source was, and the chain stops there.

Example. Reading back what was recorded:

signer.AddIngredient("original.jpg", "Original photograph", "parentOf"); C2PAIngredient added = signer.Ingredients[0]; Console.WriteLine(added.Title + " (" + added.Format + ") " + added.Relationship); if (added.ManifestLabel.Length > 0) { Console.WriteLine(" its own manifest travels along: " + added.ManifestLabel); } else { Console.WriteLine(" the source carried no manifest; the chain stops here"); }

This property is not available at design time.

Data Type

IPWorksLLMC2PAIngredient

InputData Property (C2PASigner Class)

The asset to process, held in memory.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetInputData(char* &lpInputData, int &lenInputData);
int SetInputData(const char* lpInputData, int lenInputData);

Unicode (Windows)
INT GetInputData(LPSTR &lpInputData, INT &lenInputData);
INT SetInputData(LPCSTR lpInputData, INT lenInputData);

int ipworksllm_c2pasigner_getinputdata(void* lpObj, char** lpInputData, int* lenInputData);
int ipworksllm_c2pasigner_setinputdata(void* lpObj, const char* lpInputData, int lenInputData);

QByteArray getInputData();
int setInputData(QByteArray qbaInputData);

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 InputFile and this property are set, InputFile takes precedence.

Data Type

Binary String

InputFile Property (C2PASigner Class)

The asset to process.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetInputFile();
int SetInputFile(const char* lpszInputFile);

Unicode (Windows)
LPWSTR GetInputFile();
INT SetInputFile(LPCWSTR lpszInputFile);

char* ipworksllm_c2pasigner_getinputfile(void* lpObj);
int ipworksllm_c2pasigner_setinputfile(void* lpObj, const char* lpszInputFile);

QString getInputFile();
int setInputFile(QString qsInputFile);

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 InputData are set, this property takes precedence.

Data Type

String

OutputData Property (C2PASigner Class)

The signed asset, held in memory.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetOutputData(char* &lpOutputData, int &lenOutputData);

Unicode (Windows)
INT GetOutputData(LPSTR &lpOutputData, INT &lenOutputData);

int ipworksllm_c2pasigner_getoutputdata(void* lpObj, char** lpOutputData, int* lenOutputData);

QByteArray getOutputData();

Default Value

""

Remarks

This property holds the signed asset after the operation completes, when OutputFile was left empty.

This property is read-only.

Data Type

Binary String

OutputFile Property (C2PASigner Class)

The file to write the signed asset to.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetOutputFile();
int SetOutputFile(const char* lpszOutputFile);

Unicode (Windows)
LPWSTR GetOutputFile();
INT SetOutputFile(LPCWSTR lpszOutputFile);

char* ipworksllm_c2pasigner_getoutputfile(void* lpObj);
int ipworksllm_c2pasigner_setoutputfile(void* lpObj, const char* lpszOutputFile);

QString getOutputFile();
int setOutputFile(QString qsOutputFile);

Default Value

""

Remarks

This property specifies where the signed asset is written. Set it to the full or relative path of the destination file.

If this property is empty, the signed asset is written to OutputData instead.

An error is thrown if the file already exists and Overwrite is False.

Data Type

String

Overwrite Property (C2PASigner Class)

Whether the class may overwrite an existing output file.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetOverwrite();
int SetOverwrite(int bOverwrite);

Unicode (Windows)
BOOL GetOverwrite();
INT SetOverwrite(BOOL bOverwrite);

int ipworksllm_c2pasigner_getoverwrite(void* lpObj);
int ipworksllm_c2pasigner_setoverwrite(void* lpObj, int bOverwrite);

bool getOverwrite();
int setOverwrite(bool bOverwrite);

Default Value

FALSE

Remarks

This property indicates whether the class will overwrite OutputFile. When it is False, an error is thrown if OutputFile already exists.

The default value is False.

Data Type

Boolean

SignatureAlgorithm Property (C2PASigner Class)

The algorithm used to sign the claim.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetSignatureAlgorithm();
int SetSignatureAlgorithm(const char* lpszSignatureAlgorithm);

Unicode (Windows)
LPWSTR GetSignatureAlgorithm();
INT SetSignatureAlgorithm(LPCWSTR lpszSignatureAlgorithm);

char* ipworksllm_c2pasigner_getsignaturealgorithm(void* lpObj);
int ipworksllm_c2pasigner_setsignaturealgorithm(void* lpObj, const char* lpszSignatureAlgorithm);

QString getSignatureAlgorithm();
int setSignatureAlgorithm(QString qsSignatureAlgorithm);

Default Value

"ES256"

Remarks

This property specifies the signature algorithm. The C2PA specification permits only the following values, and no others:

The value must be compatible with the key in SigningCert. The default value is ES256.

This property is not available at design time.

Data Type

String

SigningCert Property (C2PASigner Class)

The certificate used to sign the C2PA Manifest.

Syntax

• C++
• C
• Qt

IPWorksLLMCertificate* GetSigningCert();
int SetSigningCert(IPWorksLLMCertificate* val);

char* ipworksllm_c2pasigner_getsigningcerteffectivedate(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertexpirationdate(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertextendedkeyusage(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertfingerprint(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertfingerprintsha1(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertfingerprintsha256(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertissuer(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertprivatekey(void* lpObj);

int ipworksllm_c2pasigner_getsigningcertprivatekeyavailable(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertprivatekeycontainer(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertpublickey(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertpublickeyalgorithm(void* lpObj);

int ipworksllm_c2pasigner_getsigningcertpublickeylength(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertserialnumber(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertsignaturealgorithm(void* lpObj);

int ipworksllm_c2pasigner_getsigningcertstore(void* lpObj, char** lpSigningCertStore, int* lenSigningCertStore);
int ipworksllm_c2pasigner_setsigningcertstore(void* lpObj, const char* lpSigningCertStore, int lenSigningCertStore);

char* ipworksllm_c2pasigner_getsigningcertstorepassword(void* lpObj);
int ipworksllm_c2pasigner_setsigningcertstorepassword(void* lpObj, const char* lpszSigningCertStorePassword);

int ipworksllm_c2pasigner_getsigningcertstoretype(void* lpObj);
int ipworksllm_c2pasigner_setsigningcertstoretype(void* lpObj, int iSigningCertStoreType);

char* ipworksllm_c2pasigner_getsigningcertsubjectaltnames(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertthumbprintmd5(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertthumbprintsha1(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertthumbprintsha256(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertusage(void* lpObj);

int ipworksllm_c2pasigner_getsigningcertusageflags(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertversion(void* lpObj);

char* ipworksllm_c2pasigner_getsigningcertsubject(void* lpObj);
int ipworksllm_c2pasigner_setsigningcertsubject(void* lpObj, const char* lpszSigningCertSubject);

int ipworksllm_c2pasigner_getsigningcertencoded(void* lpObj, char** lpSigningCertEncoded, int* lenSigningCertEncoded);
int ipworksllm_c2pasigner_setsigningcertencoded(void* lpObj, const char* lpSigningCertEncoded, int lenSigningCertEncoded);

QString getSigningCertEffectiveDate();

QString getSigningCertExpirationDate();

QString getSigningCertExtendedKeyUsage();

QString getSigningCertFingerprint();

QString getSigningCertFingerprintSHA1();

QString getSigningCertFingerprintSHA256();

QString getSigningCertIssuer();

QString getSigningCertPrivateKey();

bool getSigningCertPrivateKeyAvailable();

QString getSigningCertPrivateKeyContainer();

QString getSigningCertPublicKey();

QString getSigningCertPublicKeyAlgorithm();

int getSigningCertPublicKeyLength();

QString getSigningCertSerialNumber();

QString getSigningCertSignatureAlgorithm();

QByteArray getSigningCertStore();
int setSigningCertStore(QByteArray qbaSigningCertStore);

QString getSigningCertStorePassword();
int setSigningCertStorePassword(QString qsSigningCertStorePassword);

int getSigningCertStoreType();
int setSigningCertStoreType(int iSigningCertStoreType);

QString getSigningCertSubjectAltNames();

QString getSigningCertThumbprintMD5();

QString getSigningCertThumbprintSHA1();

QString getSigningCertThumbprintSHA256();

QString getSigningCertUsage();

int getSigningCertUsageFlags();

QString getSigningCertVersion();

QString getSigningCertSubject();
int setSigningCertSubject(QString qsSigningCertSubject);

QByteArray getSigningCertEncoded();
int setSigningCertEncoded(QByteArray qbaSigningCertEncoded);

Remarks

This property specifies the certificate used to sign the claim. The certificate must have an associated private key.

The C2PA specification requires that a claim signing certificate carry the c2pa-kp-claimSigning extended key usage, OID 1.3.6.1.4.1.62558.2.1. A certificate without it will be rejected by conforming validators even though the signature itself is well formed.

The full chain presented with the certificate is embedded in the signature, so a validator can build a path to its own trust anchors without fetching intermediates.

This property is not available at design time.

Data Type

IPWorksLLMCertificate

TSAURL Property (C2PASigner Class)

The address of an RFC 3161 Time Stamping Authority.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetTSAURL();
int SetTSAURL(const char* lpszTSAURL);

Unicode (Windows)
LPWSTR GetTSAURL();
INT SetTSAURL(LPCWSTR lpszTSAURL);

char* ipworksllm_c2pasigner_gettsaurl(void* lpObj);
int ipworksllm_c2pasigner_settsaurl(void* lpObj, const char* lpszTSAURL);

QString getTSAURL();
int setTSAURL(QString qsTSAURL);

Default Value

""

Remarks

This property specifies the Time Stamping Authority contacted during signing. When it is set, the class obtains a trusted time-stamp over the signature and embeds it in the C2PA Manifest as a countersignature.

A time-stamped signature stays verifiable after the signing certificate expires, because a validator can establish that the signature existed while the certificate was still valid. The C2PA specification recommends obtaining a time-stamp whenever a TSA can be reached at signing time.

When this property is empty, no time-stamp is requested.

When it is set and the authority cannot be reached, or returns no token, signing fails rather than producing an untimestamped Manifest. Asking for a time-stamp and quietly getting none would leave a signature that looks complete but loses its meaning the day the certificate expires.

The connection to the authority is authenticated like any other: a TSA presenting an untrusted or expired certificate is refused. There is no event for overriding that decision.

This property is not available at design time.

Data Type

String

AddAction Method (C2PASigner Class)

Records an action in the C2PA Manifest.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int AddAction(const char* lpszAction, const char* lpszDigitalSourceType, const char* lpszSoftwareAgent);

Unicode (Windows)
INT AddAction(LPCWSTR lpszAction, LPCWSTR lpszDigitalSourceType, LPCWSTR lpszSoftwareAgent);

int ipworksllm_c2pasigner_addaction(void* lpObj, const char* lpszAction, const char* lpszDigitalSourceType, const char* lpszSoftwareAgent);

int addAction(const QString& qsAction, const QString& qsDigitalSourceType, const QString& qsSoftwareAgent);

Remarks

This method appends an action to the manifest's actions assertion, creating that assertion if it does not exist yet.

Action is the C2PA action identifier, such as c2pa.created, c2pa.edited, c2pa.opened, or c2pa.placed.

DigitalSourceType describes the nature of the content the action produced. The C2PA specification requires that a digital source type accompany the c2pa.created action for every asset. Commonly used values are:

Other values defined by the IPTC digital source type vocabulary may also be used. Pass an empty string when the action does not take one; a c2pa.opened action, for example, requires none.

SoftwareAgent names the tool that performed the action.

Disclosing AI-generated content is a single call:

signer.AddAction("c2pa.created", "http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicMedia", "MyApp/1.0");

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

AddAssertion Method (C2PASigner Class)

Appends an assertion to the Assertions collection.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int AddAssertion(const char* lpszAssertionLabel, const char* lpszMediaType, const char* lpData, int lenData);

Unicode (Windows)
INT AddAssertion(LPCWSTR lpszAssertionLabel, LPCWSTR lpszMediaType, LPCSTR lpData, INT lenData);

int ipworksllm_c2pasigner_addassertion(void* lpObj, const char* lpszAssertionLabel, const char* lpszMediaType, const char* lpData, int lenData);

int addAssertion(const QString& qsAssertionLabel, const QString& qsMediaType, QByteArray& qbaData);

Remarks

This method appends a new C2PAAssertion item to the Assertions collection.

AssertionLabel is the C2PA assertion label, such as stds.schema-org.CreativeWork or stds.exif. MediaType is the payload's media type, normally application/json or application/cbor. Data is the assertion payload.

Passing the payload through verbatim keeps the API stable as the C2PA standard assertion set evolves: a new assertion type can be written without waiting for a new build of the class.

string creativeWork = "{\"@context\":\"https://schema.org\",\"@type\":\"CreativeWork\",\"author\":[{\"@type\":\"Person\",\"name\":\"Jane Doe\"}]}"; signer.AddAssertion("stds.schema-org.CreativeWork", "application/json", System.Text.Encoding.UTF8.GetBytes(creativeWork));

Use AddAction instead when recording an action, since it builds the correctly structured actions assertion for you.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

AddIngredient Method (C2PASigner Class)

Records that an asset went into the one being signed.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int AddIngredient(const char* lpszSourceFile, const char* lpszTitle, const char* lpszRelationship);

Unicode (Windows)
INT AddIngredient(LPCWSTR lpszSourceFile, LPCWSTR lpszTitle, LPCWSTR lpszRelationship);

int ipworksllm_c2pasigner_addingredient(void* lpObj, const char* lpszSourceFile, const char* lpszTitle, const char* lpszRelationship);

int addIngredient(const QString& qsSourceFile, const QString& qsTitle, const QString& qsRelationship);

Remarks

An ingredient is a source asset and the relationship it has to this one. Recording ingredients is what turns individual Manifests into a provenance chain: a consumer can follow an edited image back to the photograph it came from, and that one back to the camera that produced it.

SourceFile is the asset that went in. Title is a human-readable name for it; pass an empty string to omit it. Relationship is one of:

When the source carries a C2PA Manifest of its own, that Manifest is copied into the Manifest being written and the ingredient points at it. The chain then travels with the file: a verifier can follow it without needing the original source asset.

When the source carries no Manifest, the ingredient still records what the source was. The chain stops there, which is the truth about that asset rather than something to conceal.

Call this before Sign. Ingredients are read back through the Ingredients collection.

Example. Recording that an edited image came from a signed original:

C2PASigner signer = new C2PASigner(); signer.InputFile = "edited.jpg"; signer.OutputFile = "edited-signed.jpg"; signer.SigningCert = new Certificate(CertStoreTypes.cstPFXFile, "signer.pfx", "password", "*"); signer.ClaimGenerator = "Acme Editor/3.0"; // The photograph this edit was made from. Its Manifest travels along. signer.AddIngredient("original.jpg", "Original photograph", "parentOf"); signer.AddAction("c2pa.edited", "", "Acme Editor/3.0"); signer.Sign();

Example. Recording the sources of a generated image:

C2PASigner signer = new C2PASigner(); signer.InputFile = "generated.png"; signer.OutputFile = "generated-signed.png"; signer.SigningCert = cert; signer.ClaimGenerator = "Acme Generator/1.0"; signer.AddIngredient("reference.jpg", "Reference image", "inputTo"); // Disclose that the output is generative. signer.AddAction("c2pa.created", "http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicMedia", "Acme Generator/1.0"); signer.Sign();

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Config Method (C2PASigner Class)

Sets or retrieves a configuration setting.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* Config(const char* lpszConfigurationString);

Unicode (Windows)
LPWSTR Config(LPCWSTR lpszConfigurationString);

char* ipworksllm_c2pasigner_config(void* lpObj, const char* lpszConfigurationString);

QString config(const QString& qsConfigurationString);

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.

Error Handling (C++)

This method returns a String value ; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

Reset Method (C2PASigner Class)

This method will reset the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Reset();

Unicode (Windows)
INT Reset();

int ipworksllm_c2pasigner_reset(void* lpObj);

int reset();

Remarks

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

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Sign Method (C2PASigner Class)

Builds, signs, and embeds a C2PA Manifest.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Sign();

Unicode (Windows)
INT Sign();

int ipworksllm_c2pasigner_sign(void* lpObj);

int sign();

Remarks

This method reads the asset named by InputFile (or held in InputData), builds a C2PA Manifest from the Assertions collection, signs the claim with SigningCert, embeds the manifest into the asset, and writes the result to OutputFile (or OutputData).

The following example signs a JPEG and discloses that it was produced by a generative model.

C2PASigner signer = new C2PASigner(); signer.InputFile = "photo.jpg"; signer.OutputFile = "photo-signed.jpg"; signer.ClaimGenerator = "MyApp/1.0"; signer.SigningCert = new Certificate(CertStoreTypes.cstPFXFile, "signer.pfx", "password", "*"); signer.AddAction("c2pa.created", "http://cv.iptc.org/newscodes/digitalsourcetype/trainedAlgorithmicMedia", "MyApp/1.0"); signer.Sign();

Signing is a two-pass operation. The manifest is embedded once at a reserved size so the final byte layout of the asset is known, the content binding hash is then computed over the asset outside the manifest's own bytes, and the real signature replaces the reservation. This is what allows the hash to cover an asset that contains the manifest.

An error is thrown when SigningCert has no private key, when SignatureAlgorithm is incompatible with that key, or when the input asset is of a format the class cannot embed into.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Error Event (C2PASigner Class)

Fired when information is available about errors during data delivery.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireError(C2PASignerErrorEventParams *e);

typedef struct {
  int ErrorCode;
  const char* Description;
  int reserved;
} C2PASignerErrorEventParams;


Unicode (Windows)
virtual INT FireError(C2PASignerErrorEventParams *e);

typedef struct {
  INT ErrorCode;
  LPCWSTR Description;
  INT reserved;
} C2PASignerErrorEventParams;

#define EID_C2PASIGNER_ERROR 1

virtual INT IPWORKSLLM_CALL FireError(int &iErrorCode, char* &lpszDescription);

class C2PASignerErrorEventParams {
public:
  int errorCode();

  const QString& description();

  int eventRetVal();
  void setEventRetVal(int iRetVal);
};

// To handle, subclass C2PASigner and override this emitter function.
virtual int fireError(C2PASignerErrorEventParams *e) {...}
// Or, connect one or more slots to this signal.
void error(C2PASignerErrorEventParams *e);

Remarks

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

The ErrorCode 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.

Log Event (C2PASigner Class)

This event fires once for each log message.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireLog(C2PASignerLogEventParams *e);

typedef struct {
  int LogLevel;
  const char* Message;
  const char* LogType;
  int reserved;
} C2PASignerLogEventParams;


Unicode (Windows)
virtual INT FireLog(C2PASignerLogEventParams *e);

typedef struct {
  INT LogLevel;
  LPCWSTR Message;
  LPCWSTR LogType;
  INT reserved;
} C2PASignerLogEventParams;

#define EID_C2PASIGNER_LOG 2

virtual INT IPWORKSLLM_CALL FireLog(int &iLogLevel, char* &lpszMessage, char* &lpszLogType);

class C2PASignerLogEventParams {
public:
  int logLevel();

  const QString& message();

  const QString& logType();

  int eventRetVal();
  void setEventRetVal(int iRetVal);
};

// To handle, subclass C2PASigner and override this emitter function.
virtual int fireLog(C2PASignerLogEventParams *e) {...}
// Or, connect one or more slots to this signal.
void log(C2PASignerLogEventParams *e);

Remarks

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

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

Message is the log entry.

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

C2PAAction Type

A single action recorded in the actions assertion.

Syntax

IPWorksLLMC2PAAction (declared in ipworksllm.h)

Remarks

This type represents one entry in a C2PA Manifest's actions assertion: something that was done to the asset, by what, and what kind of content resulted.

The actions assertion is where an asset's history is written down, and it is the mechanism regulators point to for AI disclosure. An asset produced by a generative model carries a c2pa.created action whose DigitalSourceType identifies the output as trained algorithmic media.

• Action
• DigitalSourceType
• SoftwareAgent
• When

Fields

Constructors

C2PAAction()
            

C2PAAssertion Type

A single assertion recorded in a C2PA Manifest.

Syntax

IPWorksLLMC2PAAssertion (declared in ipworksllm.h)

Remarks

This type represents one assertion: a labelled statement about the asset, stored in the manifest and covered by the claim signature.

Assertions are how a C2PA Manifest says anything at all. Some describe what was done to the asset, some describe who made it, and one, the content binding, ties the manifest to the asset bytes. Each carries a label defined by the C2PA specification and a payload whose shape that label determines.

The payload is exposed as raw data rather than parsed into typed fields, so that assertion types added to the standard after this component was built can still be read and written.

• AssertionLabel
• Data
• MediaType

Fields

Constructors

C2PAAssertion()
            

C2PAIngredient Type

An asset that went into the one being described.

Syntax

IPWorksLLMC2PAIngredient (declared in ipworksllm.h)

Remarks

This type represents an ingredient: another asset that was used to produce this one, together with the relationship between them.

Ingredients are what turn individual manifests into a provenance chain. When an editor opens a photograph and places it into a composite, the composite's manifest records the photograph as an ingredient, carrying that photograph's own manifest with it. A consumer can then walk backwards through the chain to the original capture.

• Format
• InstanceId
• ManifestLabel
• Relationship
• Title

Fields

Constructors

C2PAIngredient()
            

Certificate Type

This is the digital certificate being used.

Syntax

IPWorksLLMCertificate (declared in ipworksllm.h)

Remarks

This type describes the current digital certificate. The certificate may be a public or private key. The fields are used to identify or select certificates.

• EffectiveDate
• ExpirationDate
• ExtendedKeyUsage
• Fingerprint
• FingerprintSHA1
• FingerprintSHA256
• Issuer
• PrivateKey
• PrivateKeyAvailable
• PrivateKeyContainer
• PublicKey
• PublicKeyAlgorithm
• PublicKeyLength
• SerialNumber
• SignatureAlgorithm
• Store
• StorePassword
• StoreType
• SubjectAltNames
• ThumbprintMD5
• ThumbprintSHA1
• ThumbprintSHA256
• Usage
• UsageFlags
• Version
• Subject
• Encoded

Fields

Constructors

Certificate()
            

Certificate(const char* lpEncoded, int lenEncoded)
            

Certificate(int iStoreType, const char* lpStore, int lenStore, const char* lpszStorePassword, const char* lpszSubject)
            

IPWorksLLMList Type

Syntax

IPWorksLLMList<T> (declared in ipworksllm.h)

Remarks

IPWorksLLMList is a generic class that is used to hold a collection of objects of type T, where T is one of the custom types supported by the C2PASigner class.

int GetCount() {}

int SetCount(int count) {}

T* Get(int index) {}

T* Set(int index, T* value) {}

Config Settings (C2PASigner Class)

C2PASigner Config Settings

Base Config Settings

Trappable Errors (C2PASigner Class)

Error Handling (C++)

Call the GetLastErrorCode() method to obtain the last called method's result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. Known error codes are listed below. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

C2PASigner Errors