Inconsisten length result of RSA with PKCS1 padding about openssl HOT 1 CLOSED

Your encoded array is 1024 bytes long, and it's an array of bytes, you can't treat it with strlen() as strlen is intended for "strings", hence if find 0 bytes, it will stop counting. The encoded length depends on your key length, and is < RSA_size(rsa) long.

see documentation: https://www.openssl.org/docs/manmaster/man3/RSA_public_encrypt.html

flen must be less than RSA_size(rsa) - 11 for the PKCS #1 v1.5 based padding modes, less than RSA_size(rsa) - 41 for RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rsa) for RSA_NO_PADDING. The random number generator must be seeded prior to calling RSA_public_encrypt().

RSA_public_encrypt() returns the size of the encrypted data (i.e., RSA_size(rsa)). and this is the value u should use to get length of the encrypted data.

PS. I don't think this is the right place to ask about OpenSSL itself :) you may wan't to find OpenSSL forum and ask there.

from openssl.