> This gives a range and I'm looking for exact value. Ha, OK. I missed that. But don't you think that an exact value smaller than the cipher block size might look like an hazardous 'optimization', for a very hypothetical gain ? I don't know much about EVP_CIPHER_CTX_num() use case, looks new to me (OpenSSL version > 3 ?), sorry. Regards, Michel. -----Message d'origine----- This gives a range and I'm looking for exact value. That value can be calculated using Matt's description [0]. I'm wondering if that can be done without keeping external state, just using cipher API. The "num" parameter looked like exactly what I was looking for but either I'm holding it wrong or I misunderstood its purpose. The use case I have in mind is to provide safe API that checks if the client provided buffer big enough for next call to CipherUpdate. In some cases, for example when encrypting data block by block by the client, the output buffer of one block is sufficient. I hope that clarifies the use case I have in mind. Have a nice day! Kind regards, Wiktor [0]: https://mta.openssl.org/pipermail/openssl-users/2022-November/015623.html
