Dh DataFlex Reference Documentation
Dh
Current Version: 10.1.3
Diffie-Hellman key-exchange component.
Diffie-Hellman (D-H) key exchange is a cryptographic protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel. This key can then be used to encrypt subsequent communications using a symmetric key cipher.
Synonyms of Diffie-Hellman key exchange include:
- Diffie-Hellman key agreement
- Diffie-Hellman key establishment
- Diffie-Hellman key negotiation
- exponential key exchange
Object Creation
// (Dataflex programs use the 32-bit Chilkat ActiveX) Handle hoDh
Get Create(RefClass(cComChilkatDh)) to hoDh
Properties
DebugLogFilePath
Procedure Set ComDebugLogFilePath 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.
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 True. 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.
topLastErrorHtml
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
Procedure Set ComLastMethodSuccess Boolean 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.
topLastStringResult
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.
topVerboseLogging
Procedure Set ComVerboseLogging Boolean 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.
topVersion
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 null 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 null 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 True for success, False for failure.
topSetPG
Sets explicit values for P and G. Returns True if P and G conform to the requirements for Diffie-Hellman. P is an SSH1-format bignum passed as a hexidecimalized string.
Returns True for success, False 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 }