Dsa Dart Reference Documentation

CkDsa

Current Version: 11.6.1
Requires Chilkat Bundle License

Chilkat.Dsa

Generate, import, export, sign, and verify DSA keys and signatures.

Chilkat.Dsa is the Chilkat class for DSA key generation, DSA key import/export, DSA hash signing, and DSA signature verification. It supports private and public keys in DER, PEM, encrypted PEM, XML, explicit component, and OpenSSL parameter workflows. It also exposes DSA key components as hex-encoded SSH1-format bignums and provides helpers for working with encoded hashes and signatures.

Generate DSA keys

Create DSA key pairs and parameters for workflows that still require DSA-based signing or verification.

Import and export keys

Load and save private or public DSA keys in DER, PEM, encrypted PEM, XML, component-based, and OpenSSL-compatible formats.

Sign hashes

Create DSA signatures over message digests using a loaded private key and the appropriate encoded hash input.

Verify signatures

Verify DSA signatures using a public key, encoded hash, and signature data.

Key components

Access DSA parameters and key components as hex-encoded SSH1-format bignums for low-level interoperability scenarios.

Encoded data helpers

Work with encoded hashes and signatures when applications need hex, Base64, or other textual representations of binary values.

Common pattern: Load or generate a DSA key, compute the message hash with the desired hash algorithm, then use Dsa to sign the hash with the private key or verify the signature with the public key. For new protocol designs, consider whether a more modern signature algorithm is preferred; use this class when DSA is required for compatibility.

For an extended overview, see Dsa Class Overview.

Object Creation

// pubspec.yaml:
//     dependencies:
//       chilkat: ^11.6.1

import 'package:chilkat/chilkat.dart';

// Once per process, before any other Chilkat call:
Chilkat.unlockBundle('Anything for 30-day trial');   // shorthand for CkGlobal().unlockBundle(..)

final dsa = CkDsa();
// ... the native object is released when `dsa` is garbage collected, or now with dsa.dispose().
CkDsa CkDsa()

Creates the underlying native Chilkat object. Use a CkDsa only from the isolate that created it: Chilkat objects cannot be sent between isolates. Every call is synchronous; in a Flutter app, run long operations (network, large files) inside Isolate.run, creating the Chilkat objects inside the isolate.

void dispose()

Releases the native object immediately instead of waiting for garbage collection (useful for a large CkBinData or an open socket). Calling it more than once is harmless; any other use of the object afterwards throws a StateError. isDisposed tells whether it has been called.

Errors

A method that can fail throws a ChilkatException: a method whose only outcome is success or failure returns void and throws on failure; a method producing a String or an object returns it and throws where Chilkat would have returned null. The exception carries the object's LastErrorText at the time of the failure (lastErrorText), the class and method names (className, methodName) and a one-line message. Properties never throw, and methods that answer a question (has..., is..., ...) return a plain bool.

try {
  dsa.someMethod(...);
} on ChilkatException catch (e) {
  print(e);                // CkDsa.someMethod failed: <reason>
  print(e.lastErrorText);  // the full Chilkat log of the failed call
}

Properties

DebugLogFilePath
// read/write
String get debugLogFilePath
set debugLogFilePath(String value)

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

More Information and Examples
Example showing how to use DebugLogFilePath.
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GroupSize
// read/write
int get groupSize
set groupSize(int value)

Specifies the size, in bits, of the DSA subgroup parameter Q used by the legacy GenKey method. The default is 160. This also determines the natural size of the DSA signature components r and s.

Applications should normally leave this property at its default. When an explicit standards-era (L, N) parameter pair is required, use GenKey2, where L is the bit length of P and N is the bit length of Q.

Legacy algorithm: NIST FIPS 186-5 no longer approves DSA for generating new digital signatures. Retain DSA generation and signing only for interoperability with systems or data formats that specifically require it; DSA verification remains useful for legacy signatures.

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HexG
// read-only
String get hexG

Returns the DSA domain parameter G, the generator of the subgroup of order Q modulo P.

The returned text is a hexadecimal encoding of Chilkat's SSH1-format bignum representation, which includes a two-byte bit-length prefix followed by the unsigned integer bytes.

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HexP
// read-only
String get hexP

Returns the DSA domain parameter P, the large prime modulus.

The returned text is a hexadecimal encoding of Chilkat's SSH1-format bignum representation, which includes a two-byte bit-length prefix followed by the unsigned integer bytes.

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HexQ
// read-only
String get hexQ

Returns the DSA domain parameter Q, a prime divisor of P - 1. The bit length of Q is commonly written as N and determines the range of the private value X and signature components r and s.

The returned text is a hexadecimal encoding of Chilkat's SSH1-format bignum representation, which includes a two-byte bit-length prefix followed by the unsigned integer bytes.

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HexX
// read-only
String get hexX

Returns the DSA private value X. It is present only when the object contains a private key and satisfies 0 < X < Q.

The returned text is a hexadecimal encoding of Chilkat's SSH1-format bignum representation, which includes a two-byte bit-length prefix followed by the unsigned integer bytes.

Sensitive value: Anyone who obtains X can create signatures as the key owner. Do not log, transmit, or persist this value unless it is protected as private-key material.

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HexY
// read-only
String get hexY

Returns the DSA public value Y, where Y = GX mod P. It is available when either a public or private DSA key is loaded.

The returned text is a hexadecimal encoding of Chilkat's SSH1-format bignum representation, which includes a two-byte bit-length prefix followed by the unsigned integer bytes.

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LastErrorHtml
// read-only
String get lastErrorHtml

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
// read-only
String get lastErrorText

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

More Information and Examples
Concept of LastErrorTextLastErrorText Standard Information
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LastErrorXml
// read-only
String get lastErrorXml

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastMethodSuccess
// read/write
bool get lastMethodSuccess
set lastMethodSuccess(bool value)

Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.

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UncommonOptions
// read/write
String get uncommonOptions
set uncommonOptions(String value)
Introduced in version 9.5.0.90

Reserved for uncommon or compatibility-specific options. The default is the empty string, and applications should normally leave this property unchanged unless Chilkat documentation or support identifies a specific keyword required for the target system.

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VerboseLogging
// read/write
bool get verboseLogging
set verboseLogging(bool value)

If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
// read-only
String get version

Version of the component/library, such as "10.1.0"

More Information and Examples
How to get the Chilkat version at runtime.
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Methods

FromDerBd
void fromDerBd(CkBinData bd)
Introduced in version 11.0.0

Loads a DSA private key from the DER bytes contained in the BinData object passed in bd. Returns true on successful decoding.

Private-key handling: The BinData content contains secret key material and should be cleared or released when no longer needed.

Returns normally on success; throws a ChilkatException on failure.

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FromDerFile
void fromDerFile(String path)

Loads a DSA private key from the DER-encoded file specified by path. Returns true when the file is read and decoded successfully; otherwise returns false.

Private-key handling: Restrict access to the file because it contains secret key material. Check LastErrorText when loading fails.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
Convert DSA DER Private Key to PEM
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FromEncryptedPem
void fromEncryptedPem(String password, String pemData)

Loads a DSA private key from the PEM text in pemData. password supplies the password when the PEM is encrypted. If the PEM is unencrypted, the password is ignored and the key is loaded normally.

Returns true on success and false if the PEM cannot be decoded, the password is incorrect, or the contained key is not a supported DSA private key.

Security: Do not embed production passwords in source code or log the PEM text. Prefer protected secret storage and encrypted private-key files where practical.

Returns normally on success; throws a ChilkatException on failure.

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FromPem
void fromPem(String pemData)

Loads an unencrypted DSA private key from the PEM text in pemData. On success, the object contains the private key and its corresponding public components.

Unencrypted private key: PEM armor is only a text encoding; it does not protect the private key. Treat the string as highly sensitive and use FromEncryptedPem when password-protected PEM is available.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Signature Create and Verify
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FromPublicDerBd
void fromPublicDerBd(CkBinData bd)
Introduced in version 11.0.0

Loads a DSA public key from the DER bytes contained in the BinData object passed in bd. The resulting key can verify signatures but cannot sign.

Returns normally on success; throws a ChilkatException on failure.

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FromPublicDerFile
void fromPublicDerFile(String path)

Loads a DSA public key from the DER-encoded file specified by path. Returns true when the file is read and decoded successfully; otherwise returns false.

Returns normally on success; throws a ChilkatException on failure.

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FromPublicPem
void fromPublicPem(String pemData)

Loads a DSA public key from the PEM text in pemData. Returns true when the PEM contains a supported DSA public key and is decoded successfully.

Returns normally on success; throws a ChilkatException on failure.

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FromXml
void fromXml(String xmlKey)

Loads a DSA public or private key from the XML text in xmlKey. The XML content determines whether the resulting object contains public components only or also includes the private value X.

Security: XML is only a representation format. If the XML contains X, it contains the complete private key and must be protected accordingly.

Returns normally on success; throws a ChilkatException on failure.

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GenKey
void genKey(int numBits)

Generates a new DSA key pair with a P size of numBits bits. numBits must be at least 1024 and a multiple of 64. This legacy method uses the subgroup size selected by GroupSize, whose default is 160 bits.

For explicit standard parameter pairs such as (2048, 224) or (3072, 256), use GenKey2.

Legacy algorithm: DSA signature generation is no longer approved by FIPS 186-5. Generate new DSA keys only when required for compatibility with an existing protocol, key store, or signature format.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Generate Key
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GenKey2
void genKey2(int keyLenBits, int modLenBits)
Introduced in version 9.5.0.90

Generates a new DSA key pair using an explicit (L, N) parameter-size combination. keyLenBits is L, the bit length of the prime modulus P. modLenBits is N, the bit length of the subgroup prime Q.

LNHistorical FIPS 186-4 combination
1024160Legacy
2048224 or 256Supported parameter pairs
3072256Largest listed pair
Current standards status: These combinations come from the superseded FIPS 186-4 DSA specification. FIPS 186-5 no longer approves DSA signature generation; use this method only for compatibility.

Returns normally on success; throws a ChilkatException on failure.

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GenKeyFromParamsDerBd
void genKeyFromParamsDerBd(CkBinData bd)
Introduced in version 11.0.0

Generates a new DSA key pair from OpenSSL-style DSA parameters stored as DER bytes in the BinData object passed in bd.

The supplied data contains DSA domain parameters P, Q, and G, not an existing private key. Chilkat validates or imports those parameters and generates a fresh private value X and corresponding public value Y.

Returns normally on success; throws a ChilkatException on failure.

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GenKeyFromParamsDerFile
void genKeyFromParamsDerFile(String path)

Generates a new DSA key pair from the OpenSSL-style DER DSA-parameters file specified by path.

The supplied data contains DSA domain parameters P, Q, and G, not an existing private key. Chilkat validates or imports those parameters and generates a fresh private value X and corresponding public value Y.

Returns true when the parameters are loaded and a key pair is generated successfully.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
Generate new DSA Key from OpenSSL Parameters File
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GenKeyFromParamsPem
void genKeyFromParamsPem(String pem)

Generates a new DSA key pair from OpenSSL-style DSA parameters supplied as PEM text in pem.

The supplied data contains DSA domain parameters P, Q, and G, not an existing private key. Chilkat validates or imports those parameters and generates a fresh private value X and corresponding public value Y.

Returns normally on success; throws a ChilkatException on failure.

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GenKeyFromParamsPemFile
void genKeyFromParamsPemFile(String path)

Generates a new DSA key pair from the OpenSSL-style PEM DSA-parameters file specified by path.

The supplied data contains DSA domain parameters P, Q, and G, not an existing private key. Chilkat validates or imports those parameters and generates a fresh private value X and corresponding public value Y.

A typical parameter file is PEM-armored with a BEGIN DSA PARAMETERS header. The newly generated private key can be exported with the applicable To* methods.

Returns normally on success; throws a ChilkatException on failure.

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GenKeyFromPQG
void genKeyFromPQG(String pHex, String qHex, String gHex)
Introduced in version 9.5.0.90

Generates a new DSA private/public key pair using the preselected domain parameters P, Q, and G supplied in pHex, qHex, and gHex.

Each argument is hexadecimal text in Chilkat's SSH1-format bignum representation. Chilkat generates a fresh private value X and derives Y; the supplied values are domain parameters, not an existing key pair.

Parameter provenance: Only use DSA parameters obtained from a trusted, validated source. Malformed or maliciously chosen domain parameters can undermine signature security.

Returns normally on success; throws a ChilkatException on failure.

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GetEncodedHash
String getEncodedHash(String encoding)

Returns the current Hash bytes encoded according to encoding. Use hex or base64.

This method does not compute a hash; it only converts the bytes already stored in the Hash property to text.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

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GetEncodedSignature
String getEncodedSignature(String encoding)

Returns the current Signature bytes encoded according to encoding. Use hex or base64.

After a successful SignHash call, the returned bytes are the ASN.1 DER-encoded DSA signature containing the integers r and s.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

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LoadText
String loadText(String path)

Loads the entire file specified by path and returns its contents as text using the legacy ANSI character encoding.

Encoding note: This convenience method is suitable for ASCII-compatible PEM and similar legacy text. It is not a general Unicode file reader; use an API with an explicit character encoding when UTF-8 or other Unicode text must be preserved.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

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SaveText
void saveText(String strToSave, String path)

Writes strToSave to the file specified by path using the legacy ANSI character encoding. Returns true on success.

Encoding note: This convenience method is appropriate for ASCII-compatible PEM text. It can lose characters that are not representable in the active ANSI encoding, so use an explicitly encoded text-writing API for general Unicode content.

Returns normally on success; throws a ChilkatException on failure.

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SetEncodedHash
void setEncodedHash(String encoding, String encodedHash)

Decodes encodedHash using the encoding named by encoding and stores the resulting bytes in the Hash property. Use hex or base64.

The decoded value must be the already-computed message digest that will be signed by SignHash or checked by Verify.

Returns normally on success; throws a ChilkatException on failure.

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SetEncodedSignature
void setEncodedSignature(String encoding, String encodedSig)

Decodes the signature text in encodedSig using the encoding named by encoding and stores the resulting bytes in the Signature property. Use hex or base64.

The decoded bytes are expected to contain the ASN.1 DER-encoded DSA signature. Set the corresponding Hash and public key before calling Verify.

Returns normally on success; throws a ChilkatException on failure.

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SetEncodedSignatureRS
void setEncodedSignatureRS(String encoding, String encodedR, String encodedS)

Builds the DSA signature from separately encoded r and s integer values. encoding identifies the encoding used by both encodedR and encodedS; use hex or base64.

On success, Signature contains the ASN.1 DER SEQUENCE of the two integers and is ready for use with Verify.

Returns normally on success; throws a ChilkatException on failure.

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SetKeyExplicit
void setKeyExplicit(int groupSizeInBytes, String pHex, String qHex, String gHex, String xHex)

Loads a DSA private key from explicitly supplied components. groupSizeInBytes is the size of Q in bytes. pHex, qHex, gHex, and xHex provide P, Q, G, and the private value X, respectively.

The corresponding public value Y = GX mod P is derived from the private key.

SSH1 bignums: Each component string is hexadecimal text representing an SSH1-format bignum: a two-byte bit-length prefix followed by the unsigned integer bytes.
Sensitive value: xHex contains the private key. Do not expose it in logs or transmit it over an unprotected channel.

Returns normally on success; throws a ChilkatException on failure.

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SetPubKeyExplicit
void setPubKeyExplicit(int groupSizeInBytes, String pHex, String qHex, String gHex, String yHex)

Loads a DSA public key from explicitly supplied components. groupSizeInBytes is the size of Q in bytes. pHex, qHex, gHex, and yHex provide P, Q, G, and the public value Y, respectively.

The resulting object can verify DSA signatures but cannot create them.

SSH1 bignums: Each component string is hexadecimal text representing an SSH1-format bignum: a two-byte bit-length prefix followed by the unsigned integer bytes.

Returns normally on success; throws a ChilkatException on failure.

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SignHash
void signHash()

Creates a DSA signature over the digest currently stored in Hash. A DSA private key must be loaded, and the digest must be set directly or with SetEncodedHash before this method is called.

On success, Signature contains an ASN.1 DER-encoded sequence of the DSA values r and s. Retrieve it with GetEncodedSignature or read the Signature property.

Security-critical nonce: Each DSA signature requires a secret per-signature value. Reuse or poor generation of that value can reveal the private key. Chilkat performs this generation internally; applications should not attempt to reuse signature state.
Standards status: FIPS 186-5 no longer approves DSA for generating new signatures. Use this method only for required legacy interoperability.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Signature Create and Verify
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ToDerBd
void toDerBd(CkBinData bd)
Introduced in version 11.0.0

Writes the DER-encoded DSA private key to the BinData object passed in bd. Returns true on success.

Sensitive output: The destination contains unencrypted private-key bytes after a successful call. Protect and clear it appropriately.

Returns normally on success; throws a ChilkatException on failure.

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ToDerFile
void toDerFile(String path)

Writes the loaded DSA private key to the DER file specified by path. Returns true on success.

Sensitive output: The file contains unencrypted private-key material. Apply restrictive filesystem permissions and avoid writing it to shared or temporary locations.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Generate Key
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ToEncryptedPem
String toEncryptedPem(String password)

Returns the loaded DSA private key as password-encrypted PEM text using password as the password.

Password protection: Use a strong password and protect it separately from the PEM. Encrypted PEM reduces exposure at rest but does not make it safe to log or transmit indiscriminately.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

More Information and Examples
DSA Generate KeyConvert DSA DER Private Key to PEM
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ToPem
String toPem()

Returns the loaded DSA private key as unencrypted PEM text.

Unencrypted private key: PEM armor is not encryption. Anyone who obtains this text can use the private key, so prefer ToEncryptedPem when password protection is required.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

More Information and Examples
Convert DSA DER Private Key to PEM
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ToPublicDerFile
void toPublicDerFile(String path)

Writes the public portion of the loaded DSA key to the DER file specified by path. Returns true on success.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Generate Key
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ToPublicPem
String toPublicPem()

Returns the public portion of the loaded DSA key as PEM text. Public-key PEM may be distributed to parties that need to verify signatures; it does not contain the private value X.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

More Information and Examples
DSA Generate Key
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ToXml
String toXml(bool bPublicOnly)

Returns the loaded DSA key as XML. Set bPublicOnly to true to export public components only. Set it to false to include the private component when a private key is loaded.

Security: When bPublicOnly is false, the XML can contain the private value X. Protect it as private-key material.

Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).

More Information and Examples
DSA Get Key as XML
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Verify
void verify()

Verifies the DSA signature currently stored in Signature against the digest stored in Hash, using the loaded public key. Both values must be set before calling this method.

Returns true only when the signature is valid. A false result can indicate an invalid signature, malformed input, an incompatible key, or another operational error; inspect LastErrorText when the reason matters.

Returns normally on success; throws a ChilkatException on failure.

More Information and Examples
DSA Signature Create and VerifyDSA R,S Signature Values
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VerifyKey
bool verifyKey()

Checks the mathematical validity and internal consistency of the DSA public or private key currently loaded in the object. Returns true when the key parameters and available key components pass validation.

This does not establish who owns the key, whether the key came from a trusted source, or whether it is suitable for a particular protocol.

More Information and Examples
DSA Signature Create and Verify
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