As we know Ethereum uses
ECDSA (Elliptic Curve Digital Signature Algorithm) for its public-key cryptography. Which algorithm EOS uses for encryption?
Bitcoin, Ethereum or EOS uses secp256k1 algorithm. Not approximately, but exactly same. You can derive Ethereum address from EOS private key and sign Ethereum transaction. One difference between EOS and others, EOS supports secp256r1 a.k.a prime-256 which is NIST standard and supported by Android or iOS platform libraries. You can find there are two types of key in EOS (K1, R1) and each one indicates secp256k1 or secp256r1.
EOS also uses Elliptic curve cryptography for more you can refer https://github.com/EOSIO/eosjs-ecc