C# Class SnmpSharpNet.PrivacyDES

DES privacy protocol implementation class.

SNMP Version 3 DES privacy protocol implementation. DES requires an encryption key be provided of 16 bytes in length. Class will accept longer key values (which will be trimmed to 16 bytes) but both encrypt and decrypt operations will fail if key is shorter then required value length. Decryption operation depends on USM header privacyParameters field value which is generated by the Encrypt method. Make sure privacyParameters argument value is correctly inserted into the target packet to enable SNMP agent to decrypt the message.

Inheritance: IPrivacyProtocol

显示文件 Open project: griffina/SnmpSharpNet

Protected Properties

Property	Type	Description
_salt	System.Int32

Public Methods

Method	Description
Decrypt ( byte encryptedData, int offset, int length, byte key, int engineBoots, int engineTime, byte privacyParameters ) : byte[]	Decrypt DES encrypted ScopedPdu
Encrypt ( byte unencryptedData, int offset, int length, byte key, int engineBoots, int engineTime, byte &privacyParameters, IAuthenticationDigest authDigest ) : byte[]	Encrypt ScopedPdu using DES encryption protocol
ExtendShortKey ( byte shortKey, byte password, byte engineID, IAuthenticationDigest authProtocol ) : byte[]	Operation not used by DES. Key length has to be 16 bytes of encryption/decryption operation will fail. When called, shortKey is returned.
GetEncryptedLength ( int scopedPduLength ) : int	Get final encrypted length
PasswordToKey ( byte secret, byte engineId, IAuthenticationDigest authProtocol ) : byte[]	Convert privacy password into encryption key using packet authentication hash.
PrivacyDES ( ) : System	Standard constructor.

Protected Methods

Method	Description
NextSalt ( ) : int	Returns next salt value.

Private Methods

Method	Description
GetIV ( byte privacyKey, byte salt ) : byte[]	Generate IV from the privacy key and salt value returned by GetSalt method.
GetKey ( byte privacyPassword ) : byte[]	Extract and return DES encryption key. Privacy password is 16 bytes in length. Only the first 8 bytes are used as DES password. Remaining 8 bytes are used as pre-IV value.
GetSalt ( int engineBoots ) : byte[]	Get DES encryption salt value. Salt value is generated by concatenating engineBoots value with the random integer value.

Method Details

Decrypt() public method

Decrypt DES encrypted ScopedPdu

Thrown when encrypted data is null or length == 0 Thrown when encryption key length is less then 32 byte or if privacy parameters /// argument is null or length other then 8 bytes

public Decrypt ( byte encryptedData, int offset, int length, byte key, int engineBoots, int engineTime, byte privacyParameters ) : byte[]
encryptedData	byte	Source data buffer
offset	int	Offset within the buffer to start decryption process
length	int	Length of data to decrypt
key	byte	Decryption key. Key length has to be 32 bytes in length or longer (bytes beyond 32 bytes are ignored).
engineBoots	int	Authoritative engine boots value
engineTime	int	Authoritative engine time value
privacyParameters	byte	Privacy parameters extracted from USM header
return	byte[]

Encrypt() public method

Encrypt ScopedPdu using DES encryption protocol

Thrown when encryption key is null or length of the encryption key is too short.

public Encrypt ( byte unencryptedData, int offset, int length, byte key, int engineBoots, int engineTime, byte &privacyParameters, IAuthenticationDigest authDigest ) : byte[]
unencryptedData	byte	Unencrypted ScopedPdu byte array
offset	int	Offset to start encryption
length	int	Length of data to encrypt
key	byte	Encryption key. Key has to be at least 32 bytes is length
engineBoots	int	Authoritative engine boots value
engineTime	int	Authoritative engine time value. Not used for DES
privacyParameters	byte	Privacy parameters out buffer. This field will be filled in with information /// required to decrypt the information. Output length of this field is 8 bytes and space has to be reserved /// in the USM header to store this information
authDigest	IAuthenticationDigest	Authentication digest class reference. Not used by DES and can be null.
return	byte[]

ExtendShortKey() public method

Operation not used by DES. Key length has to be 16 bytes of encryption/decryption operation will fail. When called, shortKey is returned.

public ExtendShortKey ( byte shortKey, byte password, byte engineID, IAuthenticationDigest authProtocol ) : byte[]
shortKey	byte	Encryption key
password	byte	Privacy password
engineID	byte	Authoritative engine id
authProtocol	IAuthenticationDigest	Authentication protocol class instance
return	byte[]

GetEncryptedLength() public method

Get final encrypted length

public GetEncryptedLength ( int scopedPduLength ) : int
scopedPduLength	int	BER encoded ScopedPdu data length
return	int

NextSalt() protected method

Returns next salt value.

protected NextSalt ( ) : int
return	int

PasswordToKey() public method

Convert privacy password into encryption key using packet authentication hash.

Thrown when key size is shorter then MinimumKeyLength

public PasswordToKey ( byte secret, byte engineId, IAuthenticationDigest authProtocol ) : byte[]
secret	byte	Privacy user secret
engineId	byte	Authoritative engine id of the snmp agent
authProtocol	IAuthenticationDigest	Authentication protocol
return	byte[]

PrivacyDES() public method

Standard constructor.

public PrivacyDES ( ) : System
return	System

Property Details

_salt protected_oe property

Internal salt value. As per RFC standard, salt value is initialized in the constructor and incremented by 1 for each subsequent packet.

protected Int32,System _salt
return	System.Int32