The invention discloses a method and equipment for acquiring a symmetric key, relating to the field of communication security. The method comprises the steps of: receiving and
parsing a key transmission instruction sent by an upper computer by means of the equipment to obtain a key block header field, a key block
data field and a key block MAC value; acquiring a first secret key and a second secret key according to a protective key, first preset data, second preset data, ninth preset data and tenth preset data; acquiring an encrypted key and a MAC key according to the protective key, the firstsecret key, third preset data, fourth preset data, fifth preset data, sixth preset data, seventh preset data and eighth preset data; acquiring first
plaintext data according to the encrypted key, thekey block
data field and the key block MAC value; acquiring a second MAC value according to the MAC key, the first
plaintext data, the key block header field and the second secret key; and acquiringthe symmetric key from the first
plaintext data when the second MAC value is identical with the key block MAC value, storing the symmetric key, and returning a key transmission success response to theupper computer.