Public keys are never used directly as addresses. They are hashed first — a one-way compression that shrinks data and adds a layer of quantum resistance (hash preimage attacks are harder than key recovery).

Bitcoin uses HASH160 = RIPEMD160(SHA256(pubkey)), producing a 20-byte value. Ethereum uses the last 20 bytes of Keccak-256(pubkey). This is why exposing your public key doesn't immediately expose your address's hash preimage.

SHA-256: 256-bit output, Bitcoin block hashing
RIPEMD-160: 160-bit output, address compression
Keccak-256: Ethereum's variant of SHA-3
Base58Check / Bech32: human-readable encoding with checksums

Chain	Address pipeline	Length
Bitcoin (P2PKH)	Base58Check(HASH160(pub))	26–35 chars
Ethereum	'0x' + Keccak256(pub)[12:]	42 chars
Bech32 (SegWit)	Bech32(witness program)	42–62 chars