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#include <openssl/evp.h> |
Oct 16, 2019 openssl aes-256-cbc -salt -a -d -in encrypted.txt -out plaintext.txt Asymmetric encryption. For Asymmetric encryption you must first generate your private key and extract the public key. Openssl genrsa -aes256 -out private.key 8912 openssl rsa -in private.key -pubout -out public.key To encrypt. An AES key, and an IV for symmetric encryption, are just bunchs of random bytes. So any cryptographically strong random number generator will do the trick. OpenSSL provides such a random number generator (which itself feeds on whatever the operating system provides, e.g. CryptGenRandom on Windows or /dev/random and /dev/urandom on Linux). What encryption is applied by openssl req when a config is specified? Can the algorithm be controlled? How does openssl rsa guess the right cipher for decryption? It must obviously be encoded somewhere in the data. At first it seems nice to have openssl req generate the key.
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:
- May 15, 2018 This video tutorial will show you how to use the openssl command line to encrypt and decrypt a file using a public key. We will first generate a private key then extract the public key from this.
- # openssl genrsa -aes128 -out key.pem This command uses AES 128 only to protect the RSA key pair with a passphrase, just in case an unauthorized person can get the key file. When your Apache server starts up, it must decrypt the key in memory to use it.
- 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:
Aes Key Generator
Opening and Envelope[edit]
An envelope is opened using the EVP_Open* set of functions in the following steps:
Openssl Aes Key Generation C 1
- 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
See the following code for an example:
See also[edit]
Openssl Aes Key Generation C Definition
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