"ID",Algorithm,Public Key Format,Secret Key Format,Signature Format,PKESK Format,Reference
0,Reserved,,,,,[RFC9580]
1,RSA (Encrypt or Sign) [FIPS186],"MPI(n), MPI(e) [RFC9580, Section 5.5.5.1]","MPI(d), MPI(p), MPI(q), MPI(u)","MPI(m^d mod n) [RFC9580, Section 5.2.3.1]","MPI(m^e mod n) [RFC9580, Section 5.1.3]",[RFC9580]
2,RSA Encrypt-Only [FIPS186],"MPI(n), MPI(e) [RFC9580, Section 5.5.5.1]","MPI(d), MPI(p), MPI(q), MPI(u)",N/A,"MPI(m^e mod n) [RFC9580, Section 5.1.3]",[RFC9580]
3,RSA Sign-Only [FIPS186],"MPI(n), MPI(e) [RFC9580, Section 5.5.5.1]","MPI(d), MPI(p), MPI(q), MPI(u)","MPI(m^d mod n) [RFC9580, Section 5.2.3.1]",N/A,[RFC9580]
4-15,Unassigned,,,,,
16,Elgamal (Encrypt-Only) [ELGAMAL],"MPI(p), MPI(g), MPI(y) [RFC9580, Section 5.5.5.3]",MPI(x),N/A,"MPI(g^k mod p), MPI(m * y^k mod p) [RFC9580, Section 5.1.4]",[RFC9580]
17,DSA (Digital Signature Algorithm) [FIPS186],"MPI(p), MPI(q), MPI(g), MPI(y) [RFC9580, Section 5.5.5.2]",MPI(x),"MPI(r), MPI(s) [RFC9580, Section 5.2.3.2]",N/A,[RFC9580]
18,ECDH public key algorithm,"OID, MPI(point in curve-specific point format), KDFParams [RFC9580, Sections 9.2.1 and 5.5.5.6]","MPI(value in curve-specific format) [RFC9580, Section 9.2.1]",N/A,"MPI(point in curve-specific point format), size octet, encoded key [RFC9580, Sections 9.2.1, 5.1.5, and 11.5]",[RFC9580]
19,ECDSA public key algorithm [FIPS186],"OID, MPI(point in SEC1 format) [RFC9580, Section 5.5.5.4]",MPI(value),"MPI(r), MPI(s) [RFC9580, Section 5.2.3.2]",N/A,[RFC9580]
20,Reserved (formerly Elgamal Encrypt or Sign),,,,,[RFC9580]
21,"Reserved for Diffie-Hellman (X9.42, as defined for IETF-S/MIME)",,,,,[RFC9580]
22,EdDSALegacy (deprecated),"OID, MPI(point in prefixed native format) [RFC9580, Sections 11.2.2 and 5.5.5.5]","MPI(value in curve-specific format) [RFC9580, Section 9.2.1]","MPI, MPI [RFC9580, Sections 9.2.1 and 5.2.3.3]",N/A,[RFC9580]
23,Reserved (AEDH),,,,,[RFC9580]
24,Reserved (AEDSA),,,,,[RFC9580]
25,X25519,"32 octets [RFC9580, Section 5.5.5.7]",32 octets,N/A,"32 octets, size octet, encoded key [RFC9580, Section 5.1.6]",[RFC9580]
26,X448,"56 octets [RFC9580, Section 5.5.5.8]",56 octets,N/A,"56 octets, size octet, encoded key [RFC9580, Section 5.1.7]",[RFC9580]
27,Ed25519,"32 octets [RFC9580, Section 5.5.5.9]",32 octets,"64 octets [RFC9580, Section 5.2.3.4]",,[RFC9580]
28,Ed448,"57 octets [RFC9580, Section 5.5.5.10]",57 octets,"114 octets [RFC9580, Section 5.2.3.5]",,[RFC9580]
29-99,Unassigned,,,,,
100-110,Private or Experimental Use,,,,,
111-255,Unassigned,,,,,