OpenSSL

Create private/public key pair

openssl genrsa -out mykey.pem 1024
openssl rsa -in mykey.pem -pubout > mykey.pub

Create self signed certificate

openssl genrsa -des3 -out server.key.org 1024
openssl req -new -key server.key.org -out server.csr
openssl rsa -in server.key.org -out server.key
openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

Certificate MIME type

application/x-x509-ca-cert

Decrypt file encrypted with AES

openssl enc -d -aes-256-cbc -a -in  bitcoin-wallet-keys.txt -out keys.txt