Package com.chilkatsoft.chilkat2

Class Dsa

java.lang.Object
com.chilkatsoft.chilkat2.ChilkatObject
com.chilkatsoft.chilkat2.Dsa
All Implemented Interfaces:
AutoCloseable
public class Dsa extends ChilkatObject
<section class="dsa-summary">

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.

</section>

Instances hold a native Chilkat object: close them with ChilkatObject.close() (try-with-resources) when done; an unclosed instance is freed when it becomes unreachable.

See Also:
Online reference

  • Constructor Details

    • Dsa

      public Dsa()
      Creates a new Dsa object.

  • Method Details

    • getGroupSize

      public int getGroupSize()
      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.

      Returns:
      the value of the GroupSize property

    • setGroupSize

      public void setGroupSize​(int value)
      Sets the GroupSize property; see getGroupSize().
      Parameters:
      value - the new value

    • getHexG

      public String getHexG()
      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.

      Returns:
      the value of the HexG property (read-only)

    • getHexP

      public String getHexP()
      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.

      Returns:
      the value of the HexP property (read-only)

    • getHexQ

      public String getHexQ()
      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.

      Returns:
      the value of the HexQ property (read-only)

    • getHexX

      public String getHexX()
      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.

      Returns:
      the value of the HexX property (read-only)

    • getHexY

      public String getHexY()
      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.

      Returns:
      the value of the HexY property (read-only)

    • getUncommonOptions

      public String getUncommonOptions()
      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.
      Returns:
      the value of the UncommonOptions property

    • setUncommonOptions

      public void setUncommonOptions​(String value)
      Sets the UncommonOptions property; see getUncommonOptions().
      Parameters:
      value - the new value (not null)

    • fromDerBd

      public void fromDerBd​(BinData bd)
      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.

      Parameters:
      bd - the bd argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromDerFile

      public 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.

      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromEncryptedPem

      public 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.

      Parameters:
      password - the password argument (not null)
      pemData - the pemData argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromPem

      public 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.

      Parameters:
      pemData - the pemData argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromPublicDerBd

      public void fromPublicDerBd​(BinData bd)
      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.
      Parameters:
      bd - the bd argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromPublicDerFile

      public 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.
      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromPublicPem

      public 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.
      Parameters:
      pemData - the pemData argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • fromXml

      public 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.

      Parameters:
      xmlKey - the xmlKey argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKey

      public 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.

      Parameters:
      numBits - the numBits argument
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKey2

      public void genKey2​(int keyLenBits, int modLenBits)
      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.

      L N Historical FIPS 186-4 combination

      1024 160 Legacy

      2048 224 or 256 Supported parameter pairs

      3072 256 Largest 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.

      Parameters:
      keyLenBits - the keyLenBits argument
      modLenBits - the modLenBits argument
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKeyFromPQG

      public void genKeyFromPQG​(String pHex, String qHex, String gHex)
      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.

      Parameters:
      pHex - the pHex argument (not null)
      qHex - the qHex argument (not null)
      gHex - the gHex argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKeyFromParamsDerBd

      public void genKeyFromParamsDerBd​(BinData 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.

      Parameters:
      bd - the bd argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKeyFromParamsDerFile

      public 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.

      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKeyFromParamsPem

      public 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.

      Parameters:
      pem - the pem argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genKeyFromParamsPemFile

      public 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.

      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • getEncodedHash

      public 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.

      Parameters:
      encoding - the encoding argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • getEncodedSignature

      public 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.

      Parameters:
      encoding - the encoding argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • loadText

      public 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.

      Parameters:
      path - the path argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • saveText

      public 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.

      Parameters:
      strToSave - the strToSave argument (not null)
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • setEncodedHash

      public 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.

      Parameters:
      encoding - the encoding argument (not null)
      encodedHash - the encodedHash argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • setEncodedSignature

      public 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.

      Parameters:
      encoding - the encoding argument (not null)
      encodedSig - the encodedSig argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • setEncodedSignatureRS

      public 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.

      Parameters:
      encoding - the encoding argument (not null)
      encodedR - the encodedR argument (not null)
      encodedS - the encodedS argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • setKeyExplicit

      public 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.

      Parameters:
      groupSizeInBytes - the groupSizeInBytes argument
      pHex - the pHex argument (not null)
      qHex - the qHex argument (not null)
      gHex - the gHex argument (not null)
      xHex - the xHex argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • setPubKeyExplicit

      public 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.

      Parameters:
      groupSizeInBytes - the groupSizeInBytes argument
      pHex - the pHex argument (not null)
      qHex - the qHex argument (not null)
      gHex - the gHex argument (not null)
      yHex - the yHex argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • signHash

      public 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.

      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toDerBd

      public void toDerBd​(BinData bd)
      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.

      Parameters:
      bd - the bd argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toDerFile

      public 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.

      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toEncryptedPem

      public 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.

      Parameters:
      password - the password argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toPem

      public 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.

      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toPublicDerFile

      public void toPublicDerFile​(String path)
      Writes the public portion of the loaded DSA key to the DER file specified by path. Returns true on success.
      Parameters:
      path - the path argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toPublicPem

      public 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.
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • toXml

      public String toXml​(boolean 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.

      Parameters:
      bPublicOnly - the bPublicOnly argument
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • verify

      public 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.

      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • verifyKey

      public boolean 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.

      Returns:
      the result; this method never throws ChilkatException