Openssl "data greater than mod len"

encryption openssl private-key
automaton picture automaton · Apr 21, 2014 · Viewed 25.1k times · Source

What does the "data is greater than mod len" error message mean? I have encountered this while trying to decrypt data using php's openssl_private_decrypt. How does one go about solving this issue? Been searching hours online, not getting anywhere.

Answer

jariq picture jariq · Apr 21, 2014

Asymmetric RSA keys can encrypt/decrypt only data of limited length i.e. RSAES-PKCS1-v1_5 encryption scheme defined in RFC3447 can operate on messages of length up to k - 11 octets (k is the octet length of the RSA modulus) so if you are using 2048-bit RSA key then maximum length of the plain data to be encrypted is 245 bytes.

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