The key pairs are generated on the fly; i.e. The key pairs are ephemeral (the E in DHE). Both client and server establish a session key. The server (or the client and server) then authenticate by performing signature-generation (for authentication). This has the advantage that each session needs to. Session handling is a key concept in PHP that enables user information to be persisted across all the pages of a website or app. In this post, you'll learn the basics of session handling in PHP. We'll start with an explanation of how sessions work and how they are related to cookies. A session key is any encryption key used to symmetrically encrypt one communication session only. In other words, it's a temporary key that is only used once, during one stretch of time, for encrypting and decrypting data; future conversations between the two parties would be encrypted with different session keys.
Documentation |
#include <openssl/evp.h> |
Encryption and decryption with asymmetric keys is computationally expensive. Typically then messages are not encrypted directly with such keys but are instead encrypted using a symmetric 'session' key. This key is itself then encrypted using the public key. In OpenSSL this combination is referred to as an envelope. It is also possible to encrypt the session key with multiple public keys. This way the message can be sent to a number of different recipients (one for each public key used). The session key is the same for each recipient.
The OpenSSL manual pages for dealing with envelopes can be found here: Manual:EVP_SealInit(3) and Manual:EVP_OpenInit(3)
Sealing an Envelope[edit]
An envelope is sealed using the EVP_Seal* set of functions, and an operation consists of the following steps:
- Initialise the context
- Initialise the seal operation, providing the symmetric cipher that will be used, along with the set of public keys to encrypt the session key with
- Provide the message to be encrypted.
- Complete the encryption operation
This can be seen in the following example code:
Opening and Envelope[edit]
Php Session Example
An envelope is opened using the EVP_Open* set of functions in the following steps:
- Initialise the context
- Initialise the open operation, providing the symmetric cipher that has been used, along with the private key to decrypt the session key with
- Provide the message to be decrypted and decrypt using the session key
- Complete the decryption operation
Session Key Generation In Php 2017
See the following code for an example:
Php Session Function
See also[edit]
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