# Security Transforms Perform cryptographic functions like encoding, encryption, signing, and signature verification. ## Discussion You use security transforms to assemble a chain of security-related operations that you apply to a stream of data in macOS. ## Topics ### Transforms [`SecTransformCreateReadTransformWithReadStream(_:)`](/documentation/Security/SecTransformCreateReadTransformWithReadStream(_:)) Creates a read transform from a read stream reference. [`SecTransform`](/documentation/Security/SecTransform) A Core Foundation type that represents a security transform. [`SecTransformGetTypeID()`](/documentation/Security/SecTransformGetTypeID()) Returns the unique identifier of the opaque type to which a security transform object belongs. ### Encoding [`SecEncodeTransformCreate(_:_:)`](/documentation/Security/SecEncodeTransformCreate(_:_:)) Creates an encode transform object. [`SecDecodeTransformCreate(_:_:)`](/documentation/Security/SecDecodeTransformCreate(_:_:)) Creates a decode transform object. ### Encrypting [`SecEncryptTransformCreate(_:_:)`](/documentation/Security/SecEncryptTransformCreate(_:_:)) Creates an encryption transform object. [`SecDecryptTransformCreate(_:_:)`](/documentation/Security/SecDecryptTransformCreate(_:_:)) Creates a decryption transform object. [`SecEncryptTransformGetTypeID()`](/documentation/Security/SecEncryptTransformGetTypeID()) Returns the unique identifier of the opaque type to which an encryption transform belongs. [`SecDecryptTransformGetTypeID()`](/documentation/Security/SecDecryptTransformGetTypeID()) Returns the unique identifier of the opaque type to which a decryption transform belongs. ### Signing [`SecSignTransformCreate(_:_:)`](/documentation/Security/SecSignTransformCreate(_:_:)) Creates a signing transform object. [`SecVerifyTransformCreate(_:_:_:)`](/documentation/Security/SecVerifyTransformCreate(_:_:_:)) Creates a verify transform object. [`SecDigestTransformCreate(_:_:_:)`](/documentation/Security/SecDigestTransformCreate(_:_:_:)) Creates a digest transform object. [`SecDigestTransformGetTypeID()`](/documentation/Security/SecDigestTransformGetTypeID()) Returns the unique identifier of the opaque type to which a digest transform belongs. ### Custom Transforms [`SecTransformCreate(_:_:)`](/documentation/Security/SecTransformCreate(_:_:)) Creates a transform computation object. [`SecTransformRegister(_:_:_:)`](/documentation/Security/SecTransformRegister(_:_:_:)) Registers a custom transform. [`SecTransformCreateFP`](/documentation/Security/SecTransformCreateFP) A pointer to a function that creates a new instance of a custom transform. [`SecTransformInstanceBlock`](/documentation/Security/SecTransformInstanceBlock) A block that you return from a transform creation function. [`SecTransformImplementationRef`](/documentation/Security/SecTransformImplementationRef) An opaque pointer to a block that implements an instance of a transform. ### Transform Groups [`SecTransformCreateGroupTransform()`](/documentation/Security/SecTransformCreateGroupTransform()) Creates an object that acts as a container for a set of connected transforms. [`SecTransformFindByName(_:_:)`](/documentation/Security/SecTransformFindByName(_:_:)) Finds a member of a transform group by its name. [`SecGroupTransform`](/documentation/Security/SecGroupTransform) A Core Foundation type that represents a container holding a group of transforms. [`SecGroupTransformGetTypeID()`](/documentation/Security/SecGroupTransformGetTypeID()) Returns the Core Foundation type ID for a transform group container. ### Transform Characteristics [`SecTransformSetAttribute(_:_:_:_:)`](/documentation/Security/SecTransformSetAttribute(_:_:_:_:)) Sets a static value for an attribute in a transform. [`SecTransformGetAttribute(_:_:)`](/documentation/Security/SecTransformGetAttribute(_:_:)) Gets the current value of a transform attribute. [`SecTransformCustomSetAttribute(_:_:_:_:)`](/documentation/Security/SecTransformCustomSetAttribute(_:_:_:_:)) Sets an attribute value on a custom transform. [`SecTransformCustomGetAttribute(_:_:_:)`](/documentation/Security/SecTransformCustomGetAttribute(_:_:_:)) Gets an attribute value from a custom transform. [`SecTranformCustomGetAttribute`](/documentation/Security/SecTranformCustomGetAttribute) Gets an attribute value from a custom transform. [`SecTransformPushbackAttribute(_:_:_:)`](/documentation/Security/SecTransformPushbackAttribute(_:_:_:)) Pushes a single value back for a specific attribute. [Transform Attributes](/documentation/Security/transform-attributes) Specify the attributes of a transform. [`SecTransformAttribute`](/documentation/Security/SecTransformAttribute) A direct reference to a security transform attribute. [`SecTransformStringOrAttribute`](/documentation/Security/SecTransformStringOrAttribute) A type that may be either a string or an attribute reference. [`SecTransformMetaAttributeType`](/documentation/Security/SecTransformMetaAttributeType) The keys that describe the metadata attributes of transform attributes. ### Actions [`SecTransformSetDataAction(_:_:_:)`](/documentation/Security/SecTransformSetDataAction(_:_:_:)) Changes the way a custom transform processes data. [`SecTransformSetAttributeAction(_:_:_:_:)`](/documentation/Security/SecTransformSetAttributeAction(_:_:_:_:)) Requests a callback when an attribute is set. [`SecTransformSetTransformAction(_:_:_:)`](/documentation/Security/SecTransformSetTransformAction(_:_:_:)) Changes the way that a transform deals with transform lifecycle behaviors. [`SecTransformActionBlock`](/documentation/Security/SecTransformActionBlock) A block that overrides the default behavior of a custom transform. [`SecTransformAttributeActionBlock`](/documentation/Security/SecTransformAttributeActionBlock) A block used to override the default attribute handling for when an attribute is set. [`SecTransformDataBlock`](/documentation/Security/SecTransformDataBlock) A block used to override the default data handling for a transform. [Actions](/documentation/Security/actions) Use actions to trigger particular behaviors. ### Piping [`SecTransformConnectTransforms(_:_:_:_:_:_:)`](/documentation/Security/SecTransformConnectTransforms(_:_:_:_:_:_:)) Chains transforms together. ### Execution [`SecTransformExecute(_:_:)`](/documentation/Security/SecTransformExecute(_:_:)) Executes a transform or transform group synchronously. [`SecTransformExecuteAsync(_:_:_:)`](/documentation/Security/SecTransformExecuteAsync(_:_:_:)) Executes transform or transform group asynchronously. [`SecTransformNoData()`](/documentation/Security/SecTransformNoData()) Returns an object from inside a ProcessData override that says that although no data is being returned the transform is still active and awaiting data. [`SecMessageBlock`](/documentation/Security/SecMessageBlock) A block that delivers messages during asynchronous operations. ### Import and Export [`SecTransformCopyExternalRepresentation(_:)`](/documentation/Security/SecTransformCopyExternalRepresentation(_:)) Creates a dictionary that contains enough information to be able to recreate a transform. [`SecTransformCreateFromExternalRepresentation(_:_:)`](/documentation/Security/SecTransformCreateFromExternalRepresentation(_:_:)) Creates a transform instance from a dictionary of parameters. ### Reporting Errors [`kSecTransformErrorDomain`](/documentation/Security/kSecTransformErrorDomain) The domain of any error object created by a transform on failure. [Security Transform Error Codes](/documentation/Security/security-transform-error-codes) Recognize the error codes used in error objects created by a transform on failure. [`kSecTransformPreviousErrorKey`](/documentation/Security/kSecTransformPreviousErrorKey) The key in an error’s `userInfo` dictionary whose value specifies the previous error when multiple errors occur during transform evaluation. [`kSecTransformAbortOriginatorKey`](/documentation/Security/kSecTransformAbortOriginatorKey) The key in an error’s `userInfo` dictionary whose value indicates the transform that caused the chain to abort. ## See Also [Security Transforms Programming Guide](https://developer.apple.com/library/archive/documentation/Security/Conceptual/SecTransformPG/Introduction/Introduction.html#//apple_ref/doc/uid/TP40010801) --- Copyright © 2026 Apple Inc. 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