The best replacement for md5 is sha1.

The best alternatives to md5 are rated as following:
★★★★★  sha1
★★★★  sha
★★★  sha256
★★★  crc32
★★  sha1 speed
★★  crc
★★  aes
★★  sha 512
★  md5sum
★  sha 2
★  blowfish
★  des
★  sha1 which is more secure
★  3des
★  checksum
★  sha1 php
★  crypt
  byte to byte
  sha2
  base64
  md7
  sha 1
  sha1 which is better
  sha 256
  sha1 vpn
  hmac
  cksum
  sha512
  sha-1
  sfv
  md2
  digest md5
  pgp
  sha1 encryption
  md4

Your alternative for md5 is not listed? Suggest!
Speaking about md5, one probably shouldn't forget about rsa.

Other search terms related to md5 and their ratings are:
★★★★★ rsa
You have in mind a companion for md5 and it is not yet here? Propose!



Google Trends

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md5
sha1
sha