Final answer:
Blowfish and AES are the symmetric algorithms among the given options.
Step-by-step explanation:
The symmetric algorithms among the given options are Blowfish and AES. Diffie-Hellman and RSA are both asymmetric algorithms.
Symmetric algorithms use the same key for both encryption and decryption. Blowfish and AES are widely used symmetric algorithms in the field of cryptography. They are known for their secure and efficient performance.