RSA is an asymmetric public key algorithm that has been formalized in RFC 3447. It is in widespread use in public key infrastructures (PKI) where certificates (cf. OpenSSL::X509::Certificate) often are issued on the basis of a public/private RSA key pair. Oct 25, 2019 Generate RSA private key (2048 bit) and a Certificate Signing Request (CSR) with a single command openssl req -new -newkey rsa:2048 -nodes -keyout server.key -out server.csr Convert private key to PEM format openssl rsa -in server.key -outform PEM -out server.pem.
In this article, I have explained how to do RSA Encryption and Decryption with OpenSSL Library in C.
1).Generate RSA keys with OpenSSL
2).Public Encryption and Private Decryption
3).Private Encryption and Public Decryption.
4).Encryption and Decryption Example code.
2).Public Encryption and Private Decryption
3).Private Encryption and Public Decryption.
4).Encryption and Decryption Example code.
1).Generate RSA keys with OpenSSL
Use the below command to generate RSA keys with length of 2048.
Extract public key from private.pem with the following command.
public.pem is RSA public key in PEM format.
private.pem is RSA private key in PEM format.
private.pem is RSA private key in PEM format.
2).Public Encryption and Private Decryption
Below is the OpenSSL API for Public encryption and Private decryption.
2.1 Preparing RSA Structure
For encryption and decryption we need to prepare RSA structure. Use the below function to create RSA with key buffer.
For encryption and decryption we need to prepare RSA structure. Use the below function to create RSA with key buffer.
Openssl Generate Rsa Key And Csr
Usage for public key: createRSA(“PUBLIC_KEY_BUFFER”,1);
Usage for private key: createRSA(“PRIVATE_KEY_BUFFER”,0);
Usage for private key: createRSA(“PRIVATE_KEY_BUFFER”,0);
If you want to create RSA with key file name, you can use this function
![Rsa Rsa](/uploads/1/2/6/0/126049444/493515065.png)
2.1 Public Key Encryption.
For encryption we can use padding, below is the list of supported paddings.
For encryption we can use padding, below is the list of supported paddings.
RSA_PKCS1_PADDING
PKCS #1 v1.5 padding. This currently is the most widely used mode.
RSA_PKCS1_OAEP_PADDING
EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding parameter. This mode is recommended for all new applications.
RSA_SSLV23_PADDING
PKCS #1 v1.5 padding with an SSL-specific modification that denotes that the server is SSL3 capable.
RSA_NO_PADDING
Raw RSA encryption. This mode should only be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure.
PKCS #1 v1.5 padding. This currently is the most widely used mode.
RSA_PKCS1_OAEP_PADDING
EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding parameter. This mode is recommended for all new applications.
RSA_SSLV23_PADDING
PKCS #1 v1.5 padding with an SSL-specific modification that denotes that the server is SSL3 capable.
RSA_NO_PADDING
Raw RSA encryption. This mode should only be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure.
You can use the below method, to encrypt the data with public key.
Note: public key encryption supports all the paddings.
2.2 Private Decryption.
You can use the below method to decrypt the data with private key
You can use the below method to decrypt the data with private key
3).Private Key Encryption and Public Key Decryption.
Below is the OpenSSL API for private encryption and public decryption.
Note: private key encryption supports only these paddings. RSA_PKCS1_PADDING and RSA_NO_PADDING.
3.1 Private Key Encryption.
You can use the below function for private key encryption.
You can use the below function for private key encryption.
3.2 Public Key Decryption.
You can use the below function for public key decryption.
You can use the below function for public key decryption.
![Openssl Generate Rsa Key C Openssl Generate Rsa Key C](/uploads/1/2/6/0/126049444/171974785.png)
4) Encryption and Decryption Example code.
Reference:openssl documentaion