OpenSSL unable to load Public Key

Question

Trying to encrypt a text message via command line on OSX Yosomite 10.10.2

Created public .pem key like this:

ssh-keygen -f ~/.ssh/id_rsa.pub -e -t PKCS8 > id_rsa.pem

If I try to encrypt myMessage.txt

openssl rsautl -encrypt -inkey ~/.ssh/id_rsa.pem -pubin -in ~/Desktop/myMessage.txt -out ~/Desktop/encrypted.txt

I get unable to load Public key

If I then type:

openssl asn1parse -in id_rsa.pem

Returns: Error: offset too large

But I have no idea how to fix it. What should I change to make it work?

Answer 1

Still don't know what went wrong in my question but found a solution:

1) Generate RSA key:

$ openssl genrsa -out key.pem 1024 
$ openssl rsa -in key.pem -text -noout 

2) Save public key in pub.pem file:

$ openssl rsa -in key.pem -pubout -out pub.pem 
$ openssl rsa -in pub.pem -pubin -text -noout 

3) Encrypt some data:

$ echo test test test > file.txt 
$ openssl rsautl -encrypt -inkey pub.pem -pubin -in file.txt -out file.bin 

4) Decrypt encrypted data:

$ openssl rsautl -decrypt -inkey key.pem -in file.bin 

It works like a charm

Thanks to Marek Marcola for providing the information http://openssl.6102.n7.nabble.com/Re-Can-I-use-my-own-keys-with-openssl-for-RSA-enc-dec-td12506.html

Answer 2

I had same problem when I was extracting public key from certificate.

openssl x509 -pubkey -noout -in cert.crt > pubKey.pem

Afterwards, I wanted to print information about key with command below.

openssl rsa -text -pubin -in pubKey.pem

And gets an error: unable to load Public Key

Solution

I opened pubKey.pem in notepad++ and in the Encoding menu was UCS-2 LE BOM selected. So I changed it to UTF-8 encoding. Size of pubKey.pem was half of the original one after changing encoding. Then it works like charm.

Tested in Windows and powershell