CkDh Python Programming
Reference Documentation

CkDh

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

obj = chilkat.CkDh()

Properties

# Returns an integer value
get_G( )

The generator. The value of G should be either 2 or 5.

# str is a CkString object (output)
LastErrorHtml( str )

Error information in HTML format for the last method called.

# str is a CkString object (output)
LastErrorText( str )

Error information in plain-text format for the last method called.

# str is a CkString object (output)
LastErrorXml( str )

Error information in XML format for the last method called.

# str is a CkString object (output)
get_P( str )

A "safe" large prime returned as a hex string. The hex string represent a bignum in SSH1 format.

# Returns a boolean value
get_Utf8( )

# b is a boolean (input)
put_Utf8( b )

To be documented soon...

# str is a CkString object (output)
get_Version( str )

A version string, such as "1.2.0"

Methods

# numBits is an integer (input)
# outStr is a CkString object (output)
# Returns a boolean value
CreateE( numBits, outStr )

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 True for success, False for failure.

# E is a string (input)
# outStr is a CkString object (output)
# Returns a boolean value
FindK( E, outStr )

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 True for success, False for failure.

# numBits is an integer (input)
# G is an integer (input)
# Returns a boolean value
GenPG( numBits, G )

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.

# filename is a string (input)
# Returns a boolean value
SaveLastError( filename )

Saves the last error information to an XML formatted file.

# p is a string (input)
# g is an integer (input)
# Returns a boolean value
SetPG( p, g )

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.

# index is an integer (input)
UseKnownPrime( index )

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 }

# numBits is an integer (input)
# Returns a string
createE( numBits )

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.

# E is a string (input)
# Returns a string
findK( E )

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 string
lastErrorHtml( )

Error information in HTML format for the last method called.

# Returns a string
lastErrorText( )

Error information in plain-text format for the last method called.

# Returns a string
lastErrorXml( )

Error information in XML format for the last method called.

# Returns a string
p( )

A "safe" large prime returned as a hex string. The hex string represent a bignum in SSH1 format.

# Returns a string
version( )

A version string, such as "1.2.0"

CkDh Python ProgrammingReference Documentation

CkDh

CkDh Python Programming
Reference Documentation