Dsa Lua Reference Documentation
chilkat.Dsa
Current Version: 11.7.0
Markdown version of this page for AI tools (v 11.7.0) · all AI docs
Chilkat.Dsa
Create DSA key pairs and parameters for workflows that still require
DSA-based signing or verification.
Load and save private or public DSA keys in DER, PEM, encrypted PEM,
XML, component-based, and OpenSSL-compatible formats.
Create DSA signatures over message digests using a loaded private key
and the appropriate encoded hash input.
Verify DSA signatures using a public key, encoded hash, and signature
data.
Access DSA parameters and key components as hex-encoded SSH1-format
bignums for low-level interoperability scenarios.
Work with encoded hashes and signatures when applications need hex,
Base64, or other textual representations of binary values.
For an extended overview, see
Dsa Class Overview.
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
Import and export keys
Sign hashes
Verify signatures
Key components
Encoded data helpers
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.
Object Creation
local chilkat = require("chilkat")
local dsa = chilkat.Dsa.new()Creates the object (chilkat.Dsa() does the same). Lua's garbage collector frees it when it is no longer referenced; dsa:dispose() frees it at once, and in Lua 5.4 and later local dsa <close> = chilkat.Dsa.new() frees it when the block ends. Calling a method of a disposed object raises an error.
Errors
A method that fails returns nil followed by the error text, as io.open does: local body, err = dsa:method(...), where err is the object's last_error_text. Wrap the call in assert() to raise an error with that text instead. Methods that answer a question return true or false, numbers are returned as they are (check last_method_success where the description says a value means failure), and property reads and writes never fail for Chilkat reasons.
Misuse raises a Lua error: a wrong argument type or a missing argument (bad argument #1 to ...), an unknown property name, a write to a read-only property, an out-of-range integer, or an object of the wrong class.
Names are Chilkat's in snake_case: QuickGetStr is quick_get_str, LastErrorText is last_error_text. Properties are fields (dsa.verbose_logging = true) and methods use the colon (dsa:method(...)). Strings are UTF-8; binary data is a Lua string of bytes. Indexes are 0-based, as in every Chilkat API. Unlocking: call chilkat.unlock_bundle("...") once at startup.
Properties
DebugLogFilePath
local strVal = dsa.debug_log_file_path
dsa.debug_log_file_path = strVal
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.
GroupSize
local intVal = dsa.group_size
dsa.group_size = intVal
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.
HexG
local strVal = dsa.hex_g
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.
topHexP
local strVal = dsa.hex_p
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.
topHexQ
local strVal = dsa.hex_q
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.
topHexX
local strVal = dsa.hex_x
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.
X can create signatures as the key owner. Do not log, transmit, or persist this value unless it is protected as private-key material.HexY
local strVal = dsa.hex_y
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.
topLastErrorHtml
local strVal = dsa.last_error_html
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.
topLastErrorText
local strVal = dsa.last_error_text
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.
LastErrorXml
local strVal = dsa.last_error_xml
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.
topLastMethodSuccess
local boolVal = dsa.last_method_success
dsa.last_method_success = boolVal
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.
UncommonOptions
local strVal = dsa.uncommon_options
dsa.uncommon_options = strVal
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.
topVerboseLogging
local boolVal = dsa.verbose_logging
dsa.verbose_logging = boolVal
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.
Version
local strVal = dsa.version
Methods
FromDerBd
-- ok is true, or nil and err on failure
local ok, err = dsa:from_der_bd(bd)
Loads a DSA private key from the DER bytes contained in the BinData object passed in bdtrue on successful decoding.
BinData content contains secret key material and should be cleared or released when no longer needed.Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromDerFile
-- ok is true, or nil and err on failure
local ok, err = dsa:from_der_file(path)
Loads a DSA private key from the DER-encoded file specified by pathtrue when the file is read and decoded successfully; otherwise returns false.
LastErrorText when loading fails.Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromEncryptedPem
-- pem_data is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:from_encrypted_pem(password, pem_data)
Loads a DSA private key from the PEM text in pem_datapassword
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.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromPem
-- ok is true, or nil and err on failure
local ok, err = dsa:from_pem(pem_data)
Loads an unencrypted DSA private key from the PEM text in pem_data
FromEncryptedPem when password-protected PEM is available.Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromPublicDerBd
-- ok is true, or nil and err on failure
local ok, err = dsa:from_public_der_bd(bd)
Loads a DSA public key from the DER bytes contained in the BinData object passed in bd
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromPublicDerFile
-- ok is true, or nil and err on failure
local ok, err = dsa:from_public_der_file(path)
Loads a DSA public key from the DER-encoded file specified by pathtrue when the file is read and decoded successfully; otherwise returns false.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromPublicPem
-- ok is true, or nil and err on failure
local ok, err = dsa:from_public_pem(pem_data)
Loads a DSA public key from the PEM text in pem_datatrue when the PEM contains a supported DSA public key and is decoded successfully.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
FromXml
-- ok is true, or nil and err on failure
local ok, err = dsa:from_xml(xml_key)
Loads a DSA public or private key from the XML text in xml_keyX.
X, it contains the complete private key and must be protected accordingly.Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKey
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key(num_bits)
Generates a new DSA key pair with a P size of num_bitsnum_bitsGroupSize, whose default is 160 bits.
For explicit standard parameter pairs such as (2048, 224) or (3072, 256), use GenKey2.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKey2
-- mod_len_bits is an integer
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key2(key_len_bits, mod_len_bits)
Generates a new DSA key pair using an explicit (L, N) parameter-size combination. key_len_bitsL, the bit length of the prime modulus P. mod_len_bitsN, the bit length of the subgroup prime Q.
| L | N | Historical FIPS 186-4 combination |
|---|---|---|
1024 | 160 | Legacy |
2048 | 224 or 256 | Supported parameter pairs |
3072 | 256 | Largest listed pair |
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKeyFromParamsDerBd
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key_from_params_der_bd(bd)
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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKeyFromParamsDerFile
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key_from_params_der_file(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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKeyFromParamsPem
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key_from_params_pem(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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKeyFromParamsPemFile
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key_from_params_pem_file(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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GenKeyFromPQG
-- q_hex is a string
-- g_hex is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:gen_key_from_pqg(p_hex, q_hex, g_hex)
Generates a new DSA private/public key pair using the preselected domain parameters P, Q, and G supplied in p_hexq_hexg_hex
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.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GetEncodedHash
-- str is a string, or nil and err on failure
local str, err = dsa:get_encoded_hash(encoding)
Returns the current Hash bytes encoded according to encodinghex or base64.
This method does not compute a hash; it only converts the bytes already stored in the Hash property to text.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GetEncodedSignature
-- str is a string, or nil and err on failure
local str, err = dsa:get_encoded_signature(encoding)
Returns the current Signature bytes encoded according to encodinghex or base64.
After a successful SignHash call, the returned bytes are the ASN.1 DER-encoded DSA signature containing the integers r and s.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
LoadText
-- str is a string, or nil and err on failure
local str, err = dsa:load_text(path)
Loads the entire file specified by path
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SaveText
-- path is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:save_text(str_to_save, path)
Writes str_to_savepathtrue on success.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetEncodedHash
-- encoded_hash is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:set_encoded_hash(encoding, encoded_hash)
Decodes encoded_hashencodingHash 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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetEncodedSignature
-- encoded_sig is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:set_encoded_signature(encoding, encoded_sig)
Decodes the signature text in encoded_sigencodingSignature 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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetEncodedSignatureRS
-- encoded_r is a string
-- encoded_s is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:set_encoded_signature_rs(encoding, encoded_r, encoded_s)
Builds the DSA signature from separately encoded r and s integer values. encodingencoded_rencoded_shex or base64.
On success, Signature contains the ASN.1 DER SEQUENCE of the two integers and is ready for use with Verify.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetKeyExplicit
-- p_hex is a string
-- q_hex is a string
-- g_hex is a string
-- x_hex is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:set_key_explicit(group_size_in_bytes, p_hex, q_hex, g_hex, x_hex)
Loads a DSA private key from explicitly supplied components. group_size_in_bytesQ in bytes. p_hexq_hexg_hexx_hexP, Q, G, and the private value X, respectively.
The corresponding public value Y = GX mod P is derived from the private key.
xHex contains the private key. Do not expose it in logs or transmit it over an unprotected channel.Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SetPubKeyExplicit
-- p_hex is a string
-- q_hex is a string
-- g_hex is a string
-- y_hex is a string
-- ok is true, or nil and err on failure
local ok, err = dsa:set_pub_key_explicit(group_size_in_bytes, p_hex, q_hex, g_hex, y_hex)
Loads a DSA public key from explicitly supplied components. group_size_in_bytesQ in bytes. p_hexq_hexg_hexy_hexP, Q, G, and the public value Y, respectively.
The resulting object can verify DSA signatures but cannot create them.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SignHash
local ok, err = dsa:sign_hash()
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.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToDerBd
-- ok is true, or nil and err on failure
local ok, err = dsa:to_der_bd(bd)
Writes the DER-encoded DSA private key to the BinData object passed in bdtrue on success.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToDerFile
-- ok is true, or nil and err on failure
local ok, err = dsa:to_der_file(path)
Writes the loaded DSA private key to the DER file specified by pathtrue on success.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToEncryptedPem
-- str is a string, or nil and err on failure
local str, err = dsa:to_encrypted_pem(password)
Returns the loaded DSA private key as password-encrypted PEM text using password
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToPem
local str, err = dsa:to_pem()
Returns the loaded DSA private key as unencrypted PEM text.
ToEncryptedPem when password protection is required.Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToPublicDerFile
-- ok is true, or nil and err on failure
local ok, err = dsa:to_public_der_file(path)
Writes the public portion of the loaded DSA key to the DER file specified by pathtrue on success.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToPublicPem
local str, err = dsa:to_public_pem()
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.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
ToXml
-- str is a string, or nil and err on failure
local str, err = dsa:to_xml(b_public_only)
Returns the loaded DSA key as XML. Set b_public_onlytrue to export public components only. Set it to false to include the private component when a private key is loaded.
b_public_onlyfalse, the XML can contain the private value X. Protect it as private-key material.Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
Verify
local ok, err = dsa: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 true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
VerifyKey
local flag = dsa:verify_key()
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.
Returns true or false: an answer, not a success flag.