DSA Class

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The DSA (Digital Signature Algorithm) class enables users to generate DSA hash signatures.

Syntax

class ipworksencrypt.DSA

Remarks

The DSA (Digital Signature Algorithm) class enables users to generate DSA hash signatures.

To begin you must either specify an existing key or create a new key. Existing private keys may be specified by setting the Key* properties. To create a new key call create_key. Alternatively an existing certificate may be specified by setting the Certificate* properties

Signing

To sign data first set key or certificate. Select the input file by setting input_file or input_message. Next call sign. The sign method will automatically compute the hash, and then sign the hash with the specified key.

Send the public key (see create_key for details), file, and hash_signature to the recipient.

To sign a hash without recomputing the hash simply set hash_value to the pre-computed hash value before calling sign.

Signature Verification

To verify a signature specify the input data using input_file or input_message. Set signer_key or signer_cert. Next set hash_signature and call verify_signature. The verify_signature method will return True if the signature was successfully verified.

To verify a hash signature without recomputing the hash simply set hash_value to the pre-computed hash value before calling verify_signature.

Hash Notes

The class will determine whether or not to recompute the hash based on the properties that are set. If a file is specified by input_file or input_message the hash will be recomputed when calling sign or verify_signature. If the hash_value property is set the class will only sign the hash or verify the hash signature. Setting input_file or input_message clears the hash_value property. Setting the hash_value property clears the input file selection.

DSA Key Notes

A DSA key is made up of a number of individual parameters. When calling create_key the Key* properties are populated with a new private and public key.

After calling sign the public key must be sent to the recipient along with hash_signature so they may perform signature verification. Likewise you must obtain the public key along with hash_signature in order to perform signature verification.

The public key consists of the following parameters:

• keyp
• keyq
• keyg
• keyy

The class also includes the key_public_key property which holds the PEM formatted public key for ease of use. This is helpful if you are in control of both signature creation and verification process. When sending the public key to a recipient note that not all implementations will support using the PEM formatted value in key_public_key in which case the individual parameters must be sent.

The private key consists of the following parameters:

• keyp
• keyq
• keyg
• keyy
• keyx

The class also include the key_private_key property which holds the PEM formatted private key for ease of use. This is helpful for storing the private key more easily..

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.

cert_encoded Property

This is the certificate (PEM/Base64 encoded).

Syntax

def get_cert_encoded() -> bytes: ...
def set_cert_encoded(value: bytes) -> None: ...

cert_encoded = property(get_cert_encoded, set_cert_encoded)

Default Value

""

Remarks

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

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

cert_store Property

This is the name of the certificate store for the client certificate.

Syntax

def get_cert_store() -> bytes: ...
def set_cert_store(value: bytes) -> None: ...

cert_store = property(get_cert_store, set_cert_store)

Default Value

"MY"

Remarks

This is the name of the certificate store for the client certificate.

The cert_store_type property denotes the type of the certificate store specified by cert_store. If the store is password protected, specify the password in cert_store_password.

cert_store is used in conjunction with the cert_subject property to specify client certificates. If cert_store has a value, and cert_subject or cert_encoded is set, a search for a certificate is initiated. Please see the 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 PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

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_cert_store_password() -> str: ...
def set_cert_store_password(value: str) -> None: ...

cert_store_password = property(get_cert_store_password, set_cert_store_password)

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.

cert_store_type Property

This is the type of certificate store for this certificate.

Syntax

def get_cert_store_type() -> int: ...
def set_cert_store_type(value: int) -> None: ...

cert_store_type = property(get_cert_store_type, set_cert_store_type)

Default Value

0

Remarks

This is 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:

cert_subject Property

This is the subject of the certificate used for client authentication.

Syntax

def get_cert_subject() -> str: ...
def set_cert_subject(value: str) -> None: ...

cert_subject = property(get_cert_subject, set_cert_subject)

Default Value

""

Remarks

This is 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=support@nsoftware.com". Common fields and their meanings are as follows:

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

hash_algorithm Property

The hash algorithm used for hash computation.

Syntax

def get_hash_algorithm() -> int: ...
def set_hash_algorithm(value: int) -> None: ...

hash_algorithm = property(get_hash_algorithm, set_hash_algorithm)

Default Value

2

Remarks

This property specifies the hash algorithm used for hash computation. This is only applicable when calling sign or verify_signature and hash_value is computed. Possible values are:

hash_signature Property

The hash signature.

Syntax

def get_hash_signature() -> bytes: ...
def set_hash_signature(value: bytes) -> None: ...

hash_signature = property(get_hash_signature, set_hash_signature)

Default Value

""

Remarks

This property holds the computed hash signature. This is populated after calling sign. This must be set before calling verify_signature.

hash_value Property

The hash value of the data.

Syntax

def get_hash_value() -> bytes: ...
def set_hash_value(value: bytes) -> None: ...

hash_value = property(get_hash_value, set_hash_value)

Default Value

""

Remarks

This property holds the computed hash value for the specified data. This is populated when calling sign or verify_signature when an input file is specified by setting input_file or input_message.

If you know the hash value prior to using the class you may specify the pre-computed hash value here.

Hash Notes

The class will determine whether or not to recompute the hash based on the properties that are set. If a file is specified by input_file or input_message the hash will be recomputed when calling sign or verify_signature. If the hash_value property is set the class will only sign the hash or verify the hash signature. Setting input_file or input_message clears the hash_value property. Setting the hash_value property clears the input file selection.

input_file Property

The file 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 file to be processed. Set this property to the full or relative path to the file which will be processed.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• input_file
• input_message

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• output_file
• output_message: The output data is written to this property if no other destination is specified.

input_message Property

The message to process.

Syntax

def get_input_message() -> bytes: ...
def set_input_message(value: bytes) -> None: ...

input_message = property(get_input_message, set_input_message)

Default Value

""

Remarks

This property specifies the message to be processed.

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• input_file
• input_message

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• output_file
• output_message: The output data is written to this property if no other destination is specified.

keyg Property

Represents the G parameter for the DSA algorithm.

Syntax

def get_keyg() -> bytes: ...
def set_keyg(value: bytes) -> None: ...

keyg = property(get_keyg, set_keyg)

Default Value

""

Remarks

Represents the G parameter for the DSA algorithm.

keyp Property

Represents the P parameter for the DSA algorithm.

Syntax

def get_keyp() -> bytes: ...
def set_keyp(value: bytes) -> None: ...

keyp = property(get_keyp, set_keyp)

Default Value

""

Remarks

Represents the P parameter for the DSA algorithm.

key_private_key Property

This property is a PEM formatted private key.

Syntax

def get_key_private_key() -> str: ...
def set_key_private_key(value: str) -> None: ...

key_private_key = property(get_key_private_key, set_key_private_key)

Default Value

""

Remarks

This property is a PEM formatted private key. The purpose of this property is to allow easier management of the private key parameters by using only a single value.

key_public_key Property

This property is a PEM formatted public key.

Syntax

def get_key_public_key() -> str: ...
def set_key_public_key(value: str) -> None: ...

key_public_key = property(get_key_public_key, set_key_public_key)

Default Value

""

Remarks

This property is a PEM formatted public key. The purpose of this property is to allow easier management of the public key parameters by using only a single value.

keyq Property

Represents the Q parameter for the DSA algorithm.

Syntax

def get_keyq() -> bytes: ...
def set_keyq(value: bytes) -> None: ...

keyq = property(get_keyq, set_keyq)

Default Value

""

Remarks

Represents the Q parameter for the DSA algorithm.

keyx Property

Represents the X parameter for the DSA algorithm.

Syntax

def get_keyx() -> bytes: ...
def set_keyx(value: bytes) -> None: ...

keyx = property(get_keyx, set_keyx)

Default Value

""

Remarks

Represents the X parameter for the DSA algorithm.

keyy Property

Represents the Y parameter for the DSA algorithm.

Syntax

def get_keyy() -> bytes: ...
def set_keyy(value: bytes) -> None: ...

keyy = property(get_keyy, set_keyy)

Default Value

""

Remarks

Represents the Y parameter for the DSA algorithm.

signer_cert_encoded Property

This is the certificate (PEM/Base64 encoded).

Syntax

def get_signer_cert_encoded() -> bytes: ...
def set_signer_cert_encoded(value: bytes) -> None: ...

signer_cert_encoded = property(get_signer_cert_encoded, set_signer_cert_encoded)

Default Value

""

Remarks

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

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

signer_cert_store Property

This is the name of the certificate store for the client certificate.

Syntax

def get_signer_cert_store() -> bytes: ...
def set_signer_cert_store(value: bytes) -> None: ...

signer_cert_store = property(get_signer_cert_store, set_signer_cert_store)

Default Value

"MY"

Remarks

This is the name of the certificate store for the client certificate.

The signer_cert_store_type property denotes the type of the certificate store specified by signer_cert_store. If the store is password protected, specify the password in signer_cert_store_password.

signer_cert_store is used in conjunction with the signer_cert_subject property to specify client certificates. If signer_cert_store has a value, and signer_cert_subject or signer_cert_encoded is set, a search for a certificate is initiated. Please see the signer_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 PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

signer_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_signer_cert_store_password() -> str: ...
def set_signer_cert_store_password(value: str) -> None: ...

signer_cert_store_password = property(get_signer_cert_store_password, set_signer_cert_store_password)

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.

signer_cert_store_type Property

This is the type of certificate store for this certificate.

Syntax

def get_signer_cert_store_type() -> int: ...
def set_signer_cert_store_type(value: int) -> None: ...

signer_cert_store_type = property(get_signer_cert_store_type, set_signer_cert_store_type)

Default Value

0

Remarks

This is 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:

signer_cert_subject Property

This is the subject of the certificate used for client authentication.

Syntax

def get_signer_cert_subject() -> str: ...
def set_signer_cert_subject(value: str) -> None: ...

signer_cert_subject = property(get_signer_cert_subject, set_signer_cert_subject)

Default Value

""

Remarks

This is 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=support@nsoftware.com". Common fields and their meanings are as follows:

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

signer_keyg Property

Represents the G parameter for the DSA algorithm.

Syntax

def get_signer_keyg() -> bytes: ...
def set_signer_keyg(value: bytes) -> None: ...

signer_keyg = property(get_signer_keyg, set_signer_keyg)

Default Value

""

Remarks

Represents the G parameter for the DSA algorithm.

signer_keyp Property

Represents the P parameter for the DSA algorithm.

Syntax

def get_signer_keyp() -> bytes: ...
def set_signer_keyp(value: bytes) -> None: ...

signer_keyp = property(get_signer_keyp, set_signer_keyp)

Default Value

""

Remarks

Represents the P parameter for the DSA algorithm.

signer_key_public_key Property

This property is a PEM formatted public key.

Syntax

def get_signer_key_public_key() -> str: ...
def set_signer_key_public_key(value: str) -> None: ...

signer_key_public_key = property(get_signer_key_public_key, set_signer_key_public_key)

Default Value

""

Remarks

This property is a PEM formatted public key. The purpose of this property is to allow easier management of the public key parameters by using only a single value.

signer_keyq Property

Represents the Q parameter for the DSA algorithm.

Syntax

def get_signer_keyq() -> bytes: ...
def set_signer_keyq(value: bytes) -> None: ...

signer_keyq = property(get_signer_keyq, set_signer_keyq)

Default Value

""

Remarks

Represents the Q parameter for the DSA algorithm.

signer_keyy Property

Represents the Y parameter for the DSA algorithm.

Syntax

def get_signer_keyy() -> bytes: ...
def set_signer_keyy(value: bytes) -> None: ...

signer_keyy = property(get_signer_keyy, set_signer_keyy)

Default Value

""

Remarks

Represents the Y parameter for the DSA algorithm.

use_hex Property

Whether HashValue and HashSignature are hex encoded.

Syntax

def get_use_hex() -> bool: ...
def set_use_hex(value: bool) -> None: ...

use_hex = property(get_use_hex, set_use_hex)

Default Value

FALSE

Remarks

This property specifies whether hash_value and hash_signature are hex encoded.

If set to True, when sign is called the class will compute the hash for the specified file and populate hash_value with the hex encoded hash value. It will then create the hash signature and populate hash_signature with the hex encoded hash signature value. If hash_value is specified directly it must be a hex encoded value.

If set to True, when verify_signature is called the class will compute the hash value for the specified file and populate hash_value with the hex encoded hash value. It will then hex decode hash_signature and verify the signature. hash_signature must hold a hex encoded value. If hash_value is specified directly it must be a hex encoded value.

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.

create_key Method

Creates a new key.

Syntax

def create_key() -> None: ...

Remarks

This method creates a new public and private key.

DSA Key Notes

A DSA key is made up of a number of individual parameters. When calling create_key the Key* properties are populated with a new private and public key.

After calling sign the public key must be sent to the recipient along with hash_signature so they may perform signature verification. Likewise you must obtain the public key along with hash_signature in order to perform signature verification.

The public key consists of the following parameters:

• keyp
• keyq
• keyg
• keyy

The class also includes the key_public_key property which holds the PEM formatted public key for ease of use. This is helpful if you are in control of both signature creation and verification process. When sending the public key to a recipient note that not all implementations will support using the PEM formatted value in key_public_key in which case the individual parameters must be sent.

The private key consists of the following parameters:

• keyp
• keyq
• keyg
• keyy
• keyx

The class also include the key_private_key property which holds the PEM formatted private key for ease of use. This is helpful for storing the private key more easily.

reset Method

Resets the class.

Syntax

def reset() -> None: ...

Remarks

When called, the class will reset all of its properties to their default values.

sign Method

Creates a hash signature.

Syntax

def sign() -> None: ...

Remarks

This method will create a hash signature.

Before calling this method specify the input file by setting input_file or input_message.

A key is required to create the hash signature. You may create a new key by calling create_key, or specify an existing key pair in key. Alternatively, a certificate may be specified by setting certificate. When this method is called the class will compute the hash for the specified file and populate hash_value. It will then create the hash signature using the specified key and populate hash_signature.

To create the hash signature without first computing the hash simply specify hash_value before calling this method.

The on_progress event will fire with updates for the hash computation progress only. The hash signature creation process is quick and does not require progress updates.

verify_signature Method

Verifies the signature for the specified data.

Syntax

def verify_signature() -> bool: ...

Remarks

This method will verify a hash signature.

Before calling this method specify the input file by setting input_file or input_message.

A public key and the hash signature are required to perform the signature verification. Specify the public key in signer_key. Alternatively, a certificate may be specified by setting signer_cert. Specify the hash signature in hash_signature.

When this method is called the class will compute the hash for the specified file and populate hash_value. It will verify the signature using the specified signer_key and hash_signature.

To verify the hash signature without first computing the hash simply specify hash_value before calling this method.

The on_progress event will fire with updates for the hash computation progress only. The hash signature verification process is quick and does not require progress updates.

on_error Event

Fired when information is available about errors during data delivery.

Syntax

class DSAErrorEventParams(object):
  @property
  def error_code() -> int: ...

  @property
  def description() -> str: ...

# In class DSA:
@property
def on_error() -> Callable[[DSAErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[DSAErrorEventParams], 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 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.

on_progress Event

Fired as progress is made.

Syntax

class DSAProgressEventParams(object):
  @property
  def bytes_processed() -> int: ...

  @property
  def percent_processed() -> int: ...

# In class DSA:
@property
def on_progress() -> Callable[[DSAProgressEventParams], None]: ...
@on_progress.setter
def on_progress(event_hook: Callable[[DSAProgressEventParams], None]) -> None: ...

Remarks

This event is fired automatically as data is processed by the class.

The PercentProcessed parameter indicates the current status of the operation.

The BytesProcessed parameter holds the total number of bytes processed so far.

DSA 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.

DSA Config Settings

Base Config Settings

DSA Errors

DSA Errors

	102   No Key specified.
	104   Cannot read or write file.
	105   Key parameters incorrect.
	106   Cannot create hash.
	113   Input data or HashValue must be specified.
	121   Invalid certificate.
	124   HashSignature must be specified.
	304   Cannot write file.
	305   Cannot read file.
	1201   Specified DSA parameters are invalid.
	1202   Missing hash value.
	1203   Public key must be specified.
	1204   Key must be specified.
	1205   HashSignature must be specified.
	1206   Invalid key size.