Convert eddsa public key fro PEM to DER

[Matt Caswell]

On 14/08/2019 11:06, Robert Moskowitz wrote:
> I googled how to convert a PEM public key to DER and only found examples for RSA
> keys.  Mine are ed25519.  I thought it would be a simple algorithm substitution:
> 
> $ openssl ed25519 -pubin -inform PEM -in $dir/private/intermediate.key.pem\
>>  -outform DER -out $dir/private/intermediate.key.der
> 
> Invalid command 'ed25519'; type "help" for a list.
> 
> So since my other commands use -algorithm, I tried:
> 
> $ openssl -algorithm $algorithm -pubin -inform PEM -in
> $dir/private/intermediate.key.pem\
>>  -outform DER -out $dir/private/intermediate.key.der
> 
> Invalid command '-algorithm'; type "help" for a list.
> 
> So what is the command to convert an ed25519 public key from DER to PEM.  The
> command I used to create the key was:
> 
>    openssl genpkey -aes256 -algorithm ed25519\
>        -outform pem -out $dir/private/intermediate.key.pem

Firstly, that command creates a private key not a public key.

So if you want to convert the above *private* key into DER then:

openssl pkey -in ed25519.pem -out ed25519.der -outform DER

If on the other hand you want to read the above *private* key and output the
associated *public* key in DER then:

openssl pkey -in ed25519.pem -out ed25519-pub.der -outform DER -pubout

Matt