Are OpenSSL byte sequences in little endian or big endian order?

Question

I'm trying to use openssl dsa implementation, but I'm very confused with the following details:

• Option '-text' of the command openssl dsa ....: the hexadecimal numbers in the output, am I correct to assume that those are the bytes, and thus they are in little-Endian order?

• Functions BN_bn2hex and BN_hex2bn, what Endianess they use?

Thanks in advance for the help.

Answer 1

OpenSSL treats all series of bytes (unsigned char arrays) as big endian.

The functions BN_bn2hex and BN_hex2bn are for converting to and from a printable format. Printable formats are always in natural reading order, which is big endian.

For non-printable format conversions like bn2bin, the documentation explicitly states that the conversion is big endian. But like I said before, the convention in OpenSSL is big endian for all series of bytes.