Question

I have two separated applications, one written in Java and other in Erlang.
Both applications send messages to each other in String format, and those messages are encrypted in the Java app and need to be decrypted in the Erlang app.

The problem is this:
I’m using RSA public/private keys to do the encryption/decryption.

If I encrypt the data and decrypt all inside the my Erlang code, everything is fine. But, I’m not able to decrypt the string coming from my java endpoint.

Here’s a simple test I’m doing:

PrivKey = "-----BEGIN RSA PRIVATE KEY----- ...",
% Data is the string I receive from Java
Data = "s013aA/SGN2iGYEbEIXXKvJiipqisRVfVEDneL8npRgThTHxTnYZESzVfCF463phPZyo5aOozisU7pwDdGKXgY8aqYZC+a3uES5muTb2RrzJ17yYku+g4S44vgIwZ9EyustZafNVGEYfgbWOYaPP/q5k683uR+MRHVqp6UbqMok=",
[PrivEntry] = public_key:pem_decode(list_to_binary(PrivKey)),
Priv = public_key:pem_entry_decode(PrivEntry),
BinData = iolist_to_binary(Data),
public_key:decrypt_private(Data, Priv).

Executing this code generates an error like this:

** exception error: decrypt_failed

I think the problem is in the format of BinData, but I couldn’t find any place saying how I encode a string to pass to decrypt_private function.

Does anyone knows how to do this? This seems simple, but is taking me a lot of time to figure out.

Thanks.

Answer 1

After digging a little bit more, I found the answer!
I needed to decode my string into a base64 binary.

PrivKey = "-----BEGIN RSA PRIVATE KEY----- ...",
% Data is the string I receive from Java
Data = "s013aA/SGN2iGYEbEIXXKvJiipqisRVfVEDneL8npRgThTHxTnYZESzVfCF463phPZyo5aOozisU7pwDdGKXgY8aqYZC+a3uES5muTb2RrzJ17yYku+g4S44vgIwZ9EyustZafNVGEYfgbWOYaPP/q5k683uR+MRHVqp6UbqMok=",
[PrivEntry] = public_key:pem_decode(list_to_binary(PrivKey)),
Priv = public_key:pem_entry_decode(PrivEntry),

BinData = base64:decode(Data), %<-- THIS IS THE MAGIC

public_key:decrypt_private(BinData, Priv).

Hope this helps other people.