Bootstrap Witness¶

typedef struct cardano_bootstrap_witness_t cardano_bootstrap_witness_t¶

The bootstrap witness proves that the transaction has the authority to spend the value from the associated Byron-era input UTxOs.

Cardano has transitioned away from this type of witness from Shelley and later eras, BootstrapWitnesses are currently deprecated.

cardano_error_t cardano_bootstrap_witness_new(cardano_ed25519_public_key_t *vkey, cardano_ed25519_signature_t *signature, cardano_buffer_t *chain_code, cardano_buffer_t *attributes, cardano_bootstrap_witness_t **bootstrap_witness)¶

Creates and initializes a new instance of a Bootstrap Witness.

This function allocates and initializes a new instance of a cardano_bootstrap_witness_t object, which is used in Cardano transactions to provide witness data Byron era addresses.

Usage Example:

cardano_ed25519_public_key_t* vkey = ...; // Assume vkey is already initialized
cardano_ed25519_signature_t* signature = ...; // Assume signature is already initialized
cardano_buffer_t* chain_code = ...; // Assume chain code is initialized
cardano_buffer_t* attributes = ...; // Assume attributes are initialized
cardano_bootstrap_witness_t* bootstrap_witness = NULL;

cardano_error_t result = cardano_bootstrap_witness_new(vkey, signature, chain_code, attributes, &bootstrap_witness);

if (result == CARDANO_SUCCESS)
{
  // Use the bootstrap_witness
  // Once done, ensure to clean up and release the bootstrap_witness
  cardano_bootstrap_witness_unref(&bootstrap_witness);
}
else
{
  printf("Failed to create the bootstrap witness.\n");
}

// Cleanup the other inputs
cardano_ed25519_public_key_unref(&vkey);
cardano_ed25519_signature_unref(&signature);
cardano_buffer_unref(&chain_code);
cardano_buffer_unref(&attributes);

Parameters:¶

cardano_ed25519_public_key_t *vkey¶: [in] A pointer to an initialized cardano_ed25519_public_key_t object representing the public verification key (VKey). This key is used to verify the cryptographic signature.
cardano_ed25519_signature_t *signature¶: [in] A pointer to an initialized cardano_ed25519_signature_t object containing the cryptographic signature. This signature is produced by signing the hash of the transaction body with the corresponding private key. The VKey is used to verify that the signature is valid and was made by the owner of the corresponding private key.
cardano_buffer_t *chain_code¶: [in] A pointer to a cardano_buffer_t containing the chain code. This is used in Hierarchical Deterministic (HD) wallet address generation for the Byron era. The chain code ensures that addresses can be deterministically derived from a master key while maintaining security.
cardano_buffer_t *attributes¶: [in] A pointer to a cardano_buffer_t object representing additional attributes used for network discrimination. These attributes are used in Byron-era addresses to include extra metadata.
cardano_bootstrap_witness_t **bootstrap_witness¶: [out] On successful initialization, this will point to a newly created cardano_bootstrap_witness_t object. This object represents a “strong reference” to the bootstrap witness, meaning that it is fully initialized and ready for use. The caller is responsible for managing the lifecycle of this object. Specifically, once the bootstrap witness is no longer needed, the caller must release it by calling cardano_bootstrap_witness_unref.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the bootstrap witness was successfully created, or an appropriate error code indicating the failure reason.

cardano_error_t cardano_bootstrap_witness_from_cbor(cardano_cbor_reader_t *reader, cardano_bootstrap_witness_t **bootstrap_witness)¶

Creates a cardano_bootstrap_witness_t from a CBOR reader.

This function parses CBOR data using a provided cardano_cbor_reader_t and constructs a cardano_bootstrap_witness_t object. It assumes that the CBOR reader is set up correctly and that the CBOR data corresponds to the structure expected for a bootstrap_witness.

Usage Example:

cardano_cbor_reader_t* reader = cardano_cbor_reader_new(cbor_data, data_size);
cardano_bootstrap_witness_t* bootstrap_witness = NULL;

cardano_error_t result = cardano_bootstrap_witness_from_cbor(reader, &bootstrap_witness);

if (result == CARDANO_SUCCESS)
{
  // Use the bootstrap_witness

  // Once done, ensure to clean up and release the bootstrap_witness
  cardano_bootstrap_witness_unref(&bootstrap_witness);
}
else
{
  const char* error = cardano_cbor_reader_get_last_error(reader);
  printf("Failed to decode bootstrap_witness: %s\n", error);
}

cardano_cbor_reader_unref(&reader); // Cleanup the CBOR reader

Note

If the function fails, the last error can be retrieved by calling cardano_cbor_reader_get_last_error with the reader. The caller is responsible for freeing the created cardano_bootstrap_witness_t object by calling cardano_bootstrap_witness_unref when it is no longer needed.

Parameters:¶

cardano_cbor_reader_t *reader¶: [in] A pointer to an initialized cardano_cbor_reader_t that is ready to read the CBOR-encoded data.
cardano_bootstrap_witness_t **bootstrap_witness¶: [out] A pointer to a pointer of cardano_bootstrap_witness_t that will be set to the address of the newly created bootstrap_witness object upon successful decoding.

Returns:¶

A cardano_error_t value indicating the outcome of the operation. Returns CARDANO_SUCCESS if the bootstrap witness were successfully created, or an appropriate error code if an error occurred.

cardano_error_t cardano_bootstrap_witness_to_cbor(const cardano_bootstrap_witness_t *bootstrap_witness, cardano_cbor_writer_t *writer)¶

Serializes bootstrap witness into CBOR format using a CBOR writer.

This function serializes the given cardano_bootstrap_witness_t object using a cardano_cbor_writer_t.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...;
cardano_cbor_writer_t* writer = cardano_cbor_writer_new();

if (writer)
{
  cardano_error_t result = cardano_bootstrap_witness_to_cbor(bootstrap_witness, writer);

  if (result == CARDANO_SUCCESS)
  {
    // Use the writer's buffer containing the serialized data
  }
  else
  {
    const char* error_message = cardano_cbor_writer_get_last_error(writer);
    printf("Serialization failed: %s\n", error_message);
  }

  cardano_cbor_writer_unref(&writer);
}

cardano_bootstrap_witness_unref(&bootstrap_witness);

Parameters:¶

const cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A constant pointer to the cardano_bootstrap_witness_t object that is to be serialized.
cardano_cbor_writer_t *writer¶: [out] A pointer to a cardano_cbor_writer_t where the CBOR serialized data will be written. The writer must already be initialized and ready to accept the data.

Returns:¶

Returns CARDANO_SUCCESS if the serialization is successful. If the bootstrap_witness or writer is NULL, returns CARDANO_ERROR_POINTER_IS_NULL.

cardano_error_t cardano_bootstrap_witness_to_cip116_json(const cardano_bootstrap_witness_t *witness, cardano_json_writer_t *writer)¶

Serializes a bootstrap witness to CIP-116 JSON.

The function writes the full JSON object, including the surrounding braces. Keys are written in the order: “attributes”, “chain_code”, “signature”, “vkey”.

Parameters:¶

const cardano_bootstrap_witness_t *witness¶: [in] Pointer to a valid cardano_bootstrap_witness_t.
cardano_json_writer_t *writer¶: [in] Pointer to a valid cardano_json_writer_t.

Returns:¶

CARDANO_SUCCESS On success. CARDANO_ERROR_POINTER_IS_NULL If witness or writer is NULL. CARDANO_ERROR_MEMORY_ALLOCATION_FAILED If memory allocation fails. Other Any error propagated from nested writers.

cardano_ed25519_public_key_t *cardano_bootstrap_witness_get_vkey(cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the verification key (VKey) from a Bootstrap Witness.

This function returns the cardano_ed25519_public_key_t object representing the public verification key (VKey) associated with a cardano_bootstrap_witness_t object. The VKey is used to verify the cryptographic signature provided in the bootstrap witness.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume bootstrap_witness is initialized
cardano_ed25519_public_key_t* vkey = cardano_bootstrap_witness_get_vkey(bootstrap_witness);

if (vkey != NULL)
{
  // Use the verification key
  // Once done, ensure to clean up and release the vkey
  cardano_ed25519_public_key_unref(&vkey);
}
else
{
  printf("Failed to retrieve the verification key.\n");
}

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to an initialized cardano_bootstrap_witness_t object from which the verification key will be retrieved.

Returns:¶

A pointer to the cardano_ed25519_public_key_t object representing the verification key. The caller is responsible for managing the lifecycle of the returned VKey. Specifically, the caller must release it by calling cardano_ed25519_public_key_unref when it is no longer needed. If bootstrap_witness is NULL, the function will return NULL.

cardano_error_t cardano_bootstrap_witness_set_vkey(cardano_bootstrap_witness_t *bootstrap_witness, cardano_ed25519_public_key_t *vkey)¶

Sets the verification key (VKey) for a Bootstrap Witness.

This function assigns a new cardano_ed25519_public_key_t object as the verification key (VKey) for the given cardano_bootstrap_witness_t object. The VKey is the public key that is used to verify the cryptographic signature in the bootstrap witness.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume bootstrap_witness is initialized
cardano_ed25519_public_key_t* vkey = ...; // Assume vkey is initialized

cardano_error_t result = cardano_bootstrap_witness_set_vkey(bootstrap_witness, vkey);

if (result == CARDANO_SUCCESS)
{
  printf("VKey set successfully.\n");
}
else
{
  printf("Failed to set the VKey.\n");
}

// Cleanup resources for the VKey as it is still owned by the caller
cardano_ed25519_public_key_unref(&vkey);

Note

The function does not take ownership of the vkey, meaning the caller is still responsible for freeing the cardano_ed25519_public_key_t object when it is no longer needed.

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [inout] A pointer to an initialized cardano_bootstrap_witness_t object to which the verification key will be assigned.
cardano_ed25519_public_key_t *vkey¶: [in] A pointer to an initialized cardano_ed25519_public_key_t object representing the new verification key. The caller retains ownership of this object and must ensure its lifecycle is properly managed.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the verification key was successfully set, or an appropriate error code if an error occurred, such as CARDANO_ERROR_POINTER_IS_NULL if either bootstrap_witness or vkey is NULL.

cardano_ed25519_signature_t *cardano_bootstrap_witness_get_signature(cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the cryptographic signature from a Bootstrap Witness.

This function retrieves the cardano_ed25519_signature_t object from a given cardano_bootstrap_witness_t object. The signature is produced by signing the hash of the transaction body using the corresponding private key (SKey), and it can be verified using the associated public key (VKey).

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume bootstrap_witness is initialized
cardano_ed25519_signature_t* signature = cardano_bootstrap_witness_get_signature(bootstrap_witness);

if (signature != NULL)
{
  // Process the signature
  cardano_ed25519_signature_unref(&signature); // Ensure to clean up the signature
}
else
{
  printf("Failed to retrieve the signature.\n");
}

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to an initialized cardano_bootstrap_witness_t object from which the signature will be retrieved.

Returns:¶

A pointer to the cardano_ed25519_signature_t object representing the signature. The returned signature is a new reference, and the caller is responsible for managing its lifecycle. Specifically, the caller must release it using cardano_ed25519_signature_unref when it is no longer needed. If bootstrap_witness is NULL, this function will return NULL.

cardano_error_t cardano_bootstrap_witness_set_signature(cardano_bootstrap_witness_t *bootstrap_witness, cardano_ed25519_signature_t *signature)¶

Sets the cryptographic signature for a Bootstrap Witness.

This function assigns a new cardano_ed25519_signature_t object to a given cardano_bootstrap_witness_t object. The signature is produced by signing the hash of the transaction body using the corresponding private key (SKey), and it can be verified using the associated public key (VKey).

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume bootstrap_witness is initialized
cardano_ed25519_signature_t* signature = ...; // Assume signature is initialized

cardano_error_t result = cardano_bootstrap_witness_set_signature(bootstrap_witness, signature);
if (result == CARDANO_SUCCESS)
{
  printf("Signature successfully set.\n");
}
else
{
  printf("Failed to set the signature.\n");
}

// Clean up
cardano_ed25519_signature_unref(&signature); // Caller still owns their reference to the signature

Note

This function increases the reference count of the signature object; therefore, the caller retains ownership of their reference and must release their copy when it is no longer needed using cardano_ed25519_signature_unref.

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [inout] A pointer to an initialized cardano_bootstrap_witness_t object to which the signature will be assigned.
cardano_ed25519_signature_t *signature¶: [in] A pointer to an initialized cardano_ed25519_signature_t object representing the signature. This parameter must not be NULL.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the signature was successfully set. Returns CARDANO_ERROR_POINTER_IS_NULL if either bootstrap_witness or signature is NULL.

cardano_buffer_t *cardano_bootstrap_witness_get_chain_code(cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the chain code associated with a Bootstrap Witness.

This function returns the chain code stored in a given cardano_bootstrap_witness_t object. The chain code is used in the derivation of HD (Hierarchical Deterministic) wallet addresses in the Byron era.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume bootstrap_witness is initialized
cardano_buffer_t* chain_code = cardano_bootstrap_witness_get_chain_code(bootstrap_witness);

if (chain_code != NULL)
{
  // Use the chain code
  // Ensure to release the chain code buffer once done
  cardano_buffer_unref(&chain_code);
}
else
{
  printf("No chain code associated with the bootstrap witness or bootstrap_witness is NULL.\n");
}

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to an initialized cardano_bootstrap_witness_t object from which to retrieve the chain code.

Returns:¶

A pointer to a cardano_buffer_t object containing the chain code bytes. The returned object is a new reference, and the caller is responsible for managing its lifecycle. Specifically, the caller must release the chain code object by calling cardano_buffer_unref when it is no longer needed. Returns NULL if the bootstrap_witness is NULL or if no chain code is associated with the witness.

cardano_error_t cardano_bootstrap_witness_set_chain_code(cardano_bootstrap_witness_t *bootstrap_witness, cardano_buffer_t *chain_code)¶

Sets the chain code for a Bootstrap Witness.

This function assigns a new chain code to the given cardano_bootstrap_witness_t object. The chain code is used in the derivation of HD (Hierarchical Deterministic) wallet addresses in the Byron era.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume initialized
cardano_buffer_t* chain_code = cardano_buffer_new(...); // Assume chain code is initialized

cardano_error_t result = cardano_bootstrap_witness_set_chain_code(bootstrap_witness, chain_code);
if (result == CARDANO_SUCCESS)
{
  printf("Chain code set successfully.\n");
}
else
{
  printf("Failed to set the chain code: %s\n", cardano_error_to_string(result));
}

// The caller retains ownership of chain_code and should free it once no longer needed
cardano_buffer_unref(&chain_code);

Note

This function increases the reference count of the chain_code object, so the caller retains ownership of their respective references and must manage their lifecycles appropriately.

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [inout] A pointer to an initialized cardano_bootstrap_witness_t object to which the chain code will be set.
cardano_buffer_t *chain_code¶: [in] A pointer to an initialized cardano_buffer_t object containing the new chain code bytes. This parameter must not be NULL.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the chain code was successfully set, or an appropriate error code if an error occurred, such as CARDANO_ERROR_POINTER_IS_NULL if any of the input pointers are NULL.

cardano_buffer_t *cardano_bootstrap_witness_get_attributes(cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the attributes from a Bootstrap Witness.

This function extracts the additional attributes used for network discrimination or other purposes from a cardano_bootstrap_witness_t object. These attributes are specific to the Byron era and are stored as a byte array.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume initialized
cardano_buffer_t* attributes = cardano_bootstrap_witness_get_attributes(bootstrap_witness);

if (attributes != NULL)
{
  // Use the attributes
  printf("Attributes size: %zu\n", cardano_buffer_get_size(attributes));

  // Ensure to release the buffer once done
  cardano_buffer_unref(&attributes);
}
else
{
  printf("No attributes found or bootstrap witness is NULL.\n");
}

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to an initialized cardano_bootstrap_witness_t object from which to retrieve the attributes.

Returns:¶

A pointer to a cardano_buffer_t object containing the attributes. The returned object is a new reference, and the caller is responsible for managing its lifecycle. Specifically, the caller must release the buffer by calling cardano_buffer_unref when it is no longer needed. If the bootstrap_witness is NULL or no attributes are set, this function returns NULL.

cardano_error_t cardano_bootstrap_witness_set_attributes(cardano_bootstrap_witness_t *bootstrap_witness, cardano_buffer_t *attributes)¶

Sets the attributes for a Bootstrap Witness.

This function assigns a new set of attributes to a cardano_bootstrap_witness_t object. The attributes are used primarily for network discrimination or other purposes in the Byron era. The attributes are stored as a byte array.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = ...; // Assume initialized
cardano_buffer_t* attributes = ...; // Assume initialized buffer containing attributes

cardano_error_t result = cardano_bootstrap_witness_set_attributes(bootstrap_witness, attributes);

if (result == CARDANO_SUCCESS)
{
  printf("Attributes successfully set for bootstrap witness.\n");
}
else
{
  printf("Failed to set attributes: %s\n", cardano_error_to_string(result));
}

// The caller must manage the lifecycle of the attributes buffer separately.
cardano_buffer_unref(&attributes);

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [inout] A pointer to an initialized cardano_bootstrap_witness_t object where the attributes will be set.
cardano_buffer_t *attributes¶: [in] A pointer to an initialized cardano_buffer_t object containing the attributes to set. The caller retains ownership of the buffer and must manage its lifecycle, including releasing it with cardano_buffer_unref when it is no longer needed. This parameter can be NULL to clear the attributes.

Returns:¶

cardano_error_t indicating the outcome of the operation. Returns CARDANO_SUCCESS if the attributes were successfully set, or an appropriate error code indicating the failure reason, such as CARDANO_ERROR_POINTER_IS_NULL if the bootstrap_witness is NULL.

void cardano_bootstrap_witness_unref(cardano_bootstrap_witness_t **bootstrap_witness)¶

Decrements the reference count of a cardano_bootstrap_witness_t object.

This function is responsible for managing the lifecycle of a cardano_bootstrap_witness_t object by decreasing its reference count. When the reference count reaches zero, the bootstrap_witness is finalized; its associated resources are released, and its memory is deallocated.

Usage Example:

cardano_bootstrap_witness_t* bootstrap_witness = cardano_bootstrap_witness_new(major, minor);

// Perform operations with the bootstrap_witness...

cardano_bootstrap_witness_unref(&bootstrap_witness);
// At this point, bootstrap_witness is NULL and cannot be used.

Note

After calling cardano_bootstrap_witness_unref, the pointer to the cardano_bootstrap_witness_t object will be set to NULL to prevent its reuse.

Parameters:¶

cardano_bootstrap_witness_t **bootstrap_witness¶: [inout] A pointer to the pointer of the bootstrap_witness object. This double indirection allows the function to set the caller’s pointer to NULL, avoiding dangling pointer issues after the object has been freed.

void cardano_bootstrap_witness_ref(cardano_bootstrap_witness_t *bootstrap_witness)¶

Increases the reference count of the cardano_bootstrap_witness_t object.

This function is used to manually increment the reference count of an cardano_bootstrap_witness_t object, indicating that another part of the code has taken ownership of it. This ensures the object remains allocated and valid until all owners have released their reference by calling cardano_bootstrap_witness_unref.

Usage Example:

// Assuming bootstrap_witness is a previously created bootstrap_witness object

cardano_bootstrap_witness_ref(bootstrap_witness);

// Now bootstrap_witness can be safely used elsewhere without worrying about premature deallocation

Note

Always ensure that for every call to cardano_bootstrap_witness_ref there is a corresponding call to cardano_bootstrap_witness_unref to prevent memory leaks.

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: A pointer to the cardano_bootstrap_witness_t object whose reference count is to be incremented.

size_t cardano_bootstrap_witness_refcount(const cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the current reference count of the cardano_bootstrap_witness_t object.

This function returns the number of active references to an cardano_bootstrap_witness_t object. It’s useful for debugging purposes or managing the lifecycle of the object in complex scenarios.

Usage Example:

// Assuming bootstrap_witness is a previously created bootstrap_witness object

size_t ref_count = cardano_bootstrap_witness_refcount(bootstrap_witness);

printf("Reference count: %zu\n", ref_count);

Warning

This function does not account for transitive references. A transitive reference occurs when an object holds a reference to another object, rather than directly to the cardano_bootstrap_witness_t. As such, the reported count may not fully represent the total number of conceptual references in cases where such transitive relationships exist.

Parameters:¶

const cardano_bootstrap_witness_t *bootstrap_witness¶: A pointer to the cardano_bootstrap_witness_t object whose reference count is queried. The object must not be NULL.

Returns:¶

The number of active references to the specified cardano_bootstrap_witness_t object. If the object is properly managed (i.e., every cardano_bootstrap_witness_ref call is matched with a cardano_bootstrap_witness_unref call), this count should reach zero right before the object is deallocated.

void cardano_bootstrap_witness_set_last_error(cardano_bootstrap_witness_t *bootstrap_witness, const char *message)¶

Sets the last error message for a given cardano_bootstrap_witness_t object.

Records an error message in the bootstrap_witness’s last_error buffer, overwriting any existing message. This is useful for storing descriptive error information that can be later retrieved. The message is truncated if it exceeds the buffer’s capacity.

Note

The error message is limited to 1023 characters, including the null terminator, due to the fixed size of the last_error buffer.

Parameters:¶

cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to the cardano_bootstrap_witness_t instance whose last error message is to be set. If NULL, the function does nothing.
const char *message¶: [in] A null-terminated string containing the error message. If NULL, the bootstrap_witness’s last_error is set to an empty string, indicating no error.

const char *cardano_bootstrap_witness_get_last_error(const cardano_bootstrap_witness_t *bootstrap_witness)¶

Retrieves the last error message recorded for a specific bootstrap_witness.

This function returns a pointer to the null-terminated string containing the last error message set by cardano_bootstrap_witness_set_last_error for the given bootstrap_witness. If no error message has been set, or if the last_error buffer was explicitly cleared, an empty string is returned, indicating no error.

Note

The returned string points to internal storage within the object and must not be modified by the caller. The string remains valid until the next call to cardano_bootstrap_witness_set_last_error for the same bootstrap_witness, or until the bootstrap_witness is deallocated.

Parameters:¶

const cardano_bootstrap_witness_t *bootstrap_witness¶: [in] A pointer to the cardano_bootstrap_witness_t instance whose last error message is to be retrieved. If the bootstrap_witness is NULL, the function returns a generic error message indicating the null bootstrap_witness.

Returns:¶

A pointer to a null-terminated string containing the last error message for the specified bootstrap_witness. If the bootstrap_witness is NULL, “Object is NULL.” is returned to indicate the error.