Asymmetric encryption on a Teensy?
Teensy4.1 has 55 digital IO (serial) pins at up to 200MHz. The USB port supports 480mbps, and ethernet is 10/100mbps. You're limited to 32 DMA channels, though (complicated but these are used to access onboard peripherals/memory). You don't have much contiguous ram, either.
Now, you haven't explained what you're doing with this data. This matters because even though the CPU is running at 600MHz, asymmetric encryption is slow. Are you trying to perform real-time encrypted communication? Are you just sending or receiving data as well?
Nothing stopping you from asymmetrically encrypting on a Teensy. You can find the source code for the OpenSSL functions RSA_public_encrypt and RSA_private_decrypt.
This question goes into calculating how many CPU cycles are needed to encrypt X bytes of data.
However, asymmetric encryption has problems: Like I said, it's slow - specifically RSA, and the size of the data you can encrypt depends on the size of your key and padding.
If you want to communicate in something resembling real-time, you want to use hybrid encryption. You should read about how TLS works; the short version is that an asymmetric handshake occurs where the two parties agree on a symmetric key. Once you decide what your data actually is, you can quantize it (eg. TLS 'chunks' are up to 16KB which are then sent as multiple TCP packets) then both parties use the symmetric key to send/receive - which can encrypt large data chunks without issue.