It is considered prudent to store the EC keys securely, to prevent OpenSSL library and tools from writing the keys unencrypted to the local file system. While it is possible to encrypt the generated key afterwards, it is considered important to prevent the key from appearing in its unencrypted form in any file. Such disclosure of the key will definitely occur if openssl ecparam -genkey is used with -out (that implies storing the unencrypted key in a file). The root cause of the issue is due to the inability to enable password protection when openssl ecparam -genkey is invoked to generate EC keys. That inability is what makes necessary the subsequent use of the "ec" tool to encrypt the generated EC keys. On the other side, the OpenSSL man pages that come with the OpenSSL installation on Red Hat Enterprise Linux 8/9 (and its derivatives), do not mention the use of a cipher other than 3DES with "ec". This ambiguity causes considerable confusion. This short post explains how to use strong AES encryption to protect the just-generated EC key with a password.
Generate an EC key, but instead of storing the result in a file, send it to the "ec" tool. Even if both the help information and man page of "ec" do not provide any information on how to request AES encryption, specify the corresponding AES cipher in the command line:
openssl ecparam -genkey -name secp384r1 | openssl ec -aes-256-cbc -out my.key
But can we employ a cipher different than 3DES and aes-256-cbc? You can answer that question by checking what is supported by your OpenSSL installation. To do that just type:
openssl --help
and analyze the output. For example, the following ciphers are supported on Red Hat Enterprise Linux 9:
aes-128-cbc aes-128-ecb aes-192-cbc aes-192-ecb aes-256-cbc aes-256-ecb aria-128-cbc aria-128-cfb aria-128-cfb1 aria-128-cfb8 aria-128-ctr aria-128-ecb aria-128-ofb aria-192-cbc aria-192-cfb aria-192-cfb1 aria-192-cfb8 aria-192-ctr aria-192-ecb aria-192-ofb aria-256-cbc aria-256-cfb aria-256-cfb1 aria-256-cfb8 aria-256-ctr aria-256-ecb aria-256-ofb base64 bf bf-cbc bf-cfb bf-ecb bf-ofb camellia-128-cbc camellia-128-ecb camellia-192-cbc camellia-192-ecb camellia-256-cbc camellia-256-ecb cast cast-cbc cast5-cbc cast5-cfb cast5-ecb cast5-ofb des des-cbc des-cfb des-ecb des-ede des-ede-cbc des-ede-cfb des-ede-ofb des-ede3 des-ede3-cbc des-ede3-cfb des-ede3-ofb des-ofb des3 desx idea idea-cbc idea-cfb idea-ecb idea-ofb rc2 rc2-40-cbc rc2-64-cbc rc2-cbc rc2-cfb rc2-ecb rc2-ofb rc4 rc4-40 rc5 rc5-cbc rc5-cfb rc5-ecb rc5-ofb seed seed-cbc seed-cfb seed-ecb seed-ofb zlib
If you're moving a file with an encrypted EC key from one system to another, make sure that the OpenSSL installation there supports the cipher you used. Otherwise, the EC key won't be decrypted.
