Dh Delphi ActiveX Reference Documentation
TChilkatDh
Current Version: 11.5.0
Chilkat.Dh
Use
Use
Use
Use
Use
The shared secret is typically used as input to a key derivation step
before being used for encryption or authentication.
For an extended overview, see
Dh Class Overview.
Perform Diffie-Hellman shared-secret key exchange.
Chilkat.Dh provides the core operations needed for
Diffie-Hellman shared-secret exchange. It allows two parties to agree on a
shared secret over an insecure channel by using common Diffie-Hellman
parameters, generating public exchange values, and computing the same shared
secret from the other party's public value.
Choose known parameters
UseKnownPrime when the application wants to use a
predefined Diffie-Hellman prime group.
Generate parameters
GenPG to generate Diffie-Hellman parameters when custom
prime and generator values are required.
Set custom P and G
SetPG when the prime and generator are already known or
have been received from another party or protocol.
Create the exchange value
CreateE to create the public Diffie-Hellman value that
is sent to the other party.
Compute the shared secret
FindK with the other party's public exchange value to
compute the shared secret.
Use the result carefully
CreateE, exchange public values with the
other party, then call FindK to compute the shared secret. The
primary methods are UseKnownPrime, GenPG,
SetPG, CreateE, and FindK.
Object Creation
var obj: TChilkatDh; ... begin obj := TChilkatDh.Create(Self); ... // When finished, free the object instance. obj.Free();
Properties
DebugLogFilePath
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.
G
The generator. The value of G should be either 2 or 5.
topLastBinaryResult
This property is mainly used in SQL Server stored procedures to retrieve binary data from the last method call that returned binary data. It is only accessible if Chilkat.Global.KeepBinaryResult is set to 1. This feature allows for the retrieval of large varbinary results in an SQL Server environment, which has restrictions on returning large data via method calls, though temp tables can handle binary properties.
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.
topLastErrorText
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
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
Indicates the success or failure of the most recent method call: 1 means success, 0 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.
LastStringResult
In SQL Server stored procedures, this property holds the string return value of the most recent method call that returns a string. It is accessible only when Chilkat.Global.KeepStringResult is set to TRUE. SQL Server has limitations on string lengths returned from methods and properties, but temp tables can be used to access large strings.
LastStringResultLen
The length, in characters, of the string contained in the LastStringResult property.
topP
A safe large prime returned as a hex string. The hex string represent a bignum in SSH1 format.
VerboseLogging
If set to 1, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is 0. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
Methods
CreateE
The 1st step in Diffie-Hellman key exchange (to generate a shared-secret). The numBits should be twice the size (in bits) of the shared secret to be generated. For example, if you are using DH to create a 128-bit AES session key, then numBits should be set to 256. Returns E as a bignum in SSH-format as a hex string.
Returns a zero-length WideString on failure
FindK
The 2nd and final step in Diffie-Hellman (DH) key exchange. E is the E created by the other party. Returns the shared secret (K) as an SSH1-format bignum encoded as a hex string.
Returns a zero-length WideString on failure
GenPG
Generates a large safe prime that is numBits bits in size using the generator G. Generating a new (random) P is expensive in both time and CPU cycles. A prime should be 1024 or more bits in length.
Returns 1 for success, 0 for failure.
topSetPG
Sets explicit values for P and G. Returns 1 if P and G conform to the requirements for Diffie-Hellman. P is an SSH1-format bignum passed as a hexidecimalized string.
Returns 1 for success, 0 for failure.
UseKnownPrime
Sets P and G to a known safe prime. The index may have the following values:
1: First Oakley Default Group from RFC2409, section 6.1. Generator is 2. The prime is: 2^768 - 2 ^704 - 1 + 2^64 * { [2^638 pi] + 149686 }
2: Prime for 2nd Oakley Group (RFC 2409) -- 1024-bit MODP Group. Generator is 2. The prime is: 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
3: 1536-bit MODP Group from RFC3526, Section 2. Generator is 2. The prime is: 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }
4: Prime for 14th Oakley Group (RFC 3526) -- 2048-bit MODP Group. Generator is 2. The prime is: 2^2048 - 2^1984 - 1 + 2^64 * { [2^1918 pi] + 124476 }
5: 3072-bit MODP Group from RFC3526, Section 4. Generator is 2. The prime is: 2^3072 - 2^3008 - 1 + 2^64 * { [2^2942 pi] + 1690314 }
6: 4096-bit MODP Group from RFC3526, Section 5. Generator is 2. The prime is: 2^4096 - 2^4032 - 1 + 2^64 * { [2^3966 pi] + 240904 }
7: 6144-bit MODP Group from RFC3526, Section 6. Generator is 2. The prime is: 2^6144 - 2^6080 - 1 + 2^64 * { [2^6014 pi] + 929484 }
8: 8192-bit MODP Group from RFC3526, Section 7. Generator is 2. The prime is: 2^8192 - 2^8128 - 1 + 2^64 * { [2^8062 pi] + 4743158 }