On Thu, Jan 4, 2024 at 11:19 AM Johannes Winkler <jwin...@gmail.com> wrote:
>
> I am working on a GUI programme for crypto++. When selecting block ciphers
> dynamically (from GUI), there is a problem to choose the cipher dynamically
> in code.
>
> Here is an example:
> let's do AES-CFB-Encryption
> CryptoPP::CFB_Mode<CryptoPP::AES>::Encryption obj;
>
> However, if I want to switch to Twofish-OFB-Decryption
> CryptoPP::OFB_Mode<CryptoPP::Twofish>::Decryption obj;
> I have to change 3 spots in this line. Unfortunately, I cannot put
> CryptoPP::AES in a variable. Is there a possibility to choose the algorithm
> like
> CryptoPP::A<B>::C obj; with A=CBC_Mode, B=AES, C=Decryption
> Or a string-based approach like Cipher("AES-CBC-Decryption")
>
> Currently, I have a if-else tree with 6 algorithms, 5 modes, Encrypt/Decrypt,
> therefore, 6x5x2=60 branches, which is annoying. Is there a better solution?
Yeah, the if-then-else is the way I do it, in code for PEM parsing.
See <https://github.com/noloader/cryptopp-pem/blob/master/pem_read.cpp#L312>.
You might be able to do it with an External Mode Cipher. Take a look
at CFB_Mode_ExternalCipher and friends:
$ grep Mode_ExternalCipher *.h
ccm.h: CTR_Mode_ExternalCipher::Encryption m_ctr;
eax.h: CTR_Mode_ExternalCipher::Encryption m_ctr;
gcm.h: class CRYPTOPP_DLL GCTR : public CTR_Mode_ExternalCipher::Encryption
modes.h:struct CFB_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct CFB_FIPS_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct OFB_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct CTR_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct ECB_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct CBC_Mode_ExternalCipher : public CipherModeDocumentation
modes.h:struct CBC_CTS_Mode_ExternalCipher : public CipherModeDocumentation
Jeff
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