diff --git a/src/activitypub/actors/attachments.rs b/src/activitypub/actors/attachments.rs
index 4cac006..9bbcb14 100644
--- a/src/activitypub/actors/attachments.rs
+++ b/src/activitypub/actors/attachments.rs
@@ -12,13 +12,13 @@ use crate::identity::{
     claims::create_identity_claim,
     did::Did,
     minisign::verify_minisign_identity_proof,
-    signatures::{PROOF_TYPE_ID_EIP191, PROOF_TYPE_ID_MINISIGN},
 };
 use crate::models::profiles::types::{
     ExtraField,
     IdentityProof,
     PaymentLink,
     PaymentOption,
+    ProofType,
 };
 use super::types::ActorAttachment;
 
@@ -30,7 +30,7 @@ pub fn attach_identity_proof(
         name: proof.issuer.to_string(),
         value: None,
         href: None,
-        signature_algorithm: Some(proof.proof_type),
+        signature_algorithm: Some(proof.proof_type.to_string()),
         signature_value: Some(proof.value),
     }
 }
@@ -43,17 +43,19 @@ pub fn parse_identity_proof(
         return Err(ValidationError("invalid attachment type"));
     };
     let proof_type = attachment.signature_algorithm.as_ref()
-        .ok_or(ValidationError("missing proof type"))?;
+        .ok_or(ValidationError("missing proof type"))?
+        .parse()
+        .map_err(|_| ValidationError("unsupported proof type"))?;
     let did = attachment.name.parse::<Did>()
-        .map_err(|_| ValidationError("invalid did"))?;
+        .map_err(|_| ValidationError("invalid DID"))?;
     let message = create_identity_claim(actor_id, &did)
         .map_err(|_| ValidationError("invalid claim"))?;
     let signature = attachment.signature_value.as_ref()
         .ok_or(ValidationError("missing signature"))?;
     match did {
         Did::Key(ref did_key) => {
-            if proof_type != PROOF_TYPE_ID_MINISIGN {
-                return Err(ValidationError("unknown proof type"));
+            if !matches!(proof_type, ProofType::LegacyMinisignIdentityProof) {
+                return Err(ValidationError("incorrect proof type"));
             };
             verify_minisign_identity_proof(
                 did_key,
@@ -62,8 +64,8 @@ pub fn parse_identity_proof(
             ).map_err(|_| ValidationError("invalid identity proof"))?;
         },
         Did::Pkh(ref did_pkh) => {
-            if proof_type != PROOF_TYPE_ID_EIP191 {
-                return Err(ValidationError("unknown proof type"));
+            if !matches!(proof_type, ProofType::LegacyEip191IdentityProof) {
+                return Err(ValidationError("incorrect proof type"));
             };
             verify_eip191_identity_proof(
                 did_pkh,
@@ -74,7 +76,7 @@ pub fn parse_identity_proof(
     };
     let proof = IdentityProof {
         issuer: did,
-        proof_type: proof_type.to_string(),
+        proof_type: proof_type,
         value: signature.to_string(),
     };
     Ok(proof)
diff --git a/src/mastodon_api/accounts/views.rs b/src/mastodon_api/accounts/views.rs
index c7ab08e..58331ac 100644
--- a/src/mastodon_api/accounts/views.rs
+++ b/src/mastodon_api/accounts/views.rs
@@ -30,7 +30,6 @@ use crate::identity::{
         parse_minisign_signature,
         verify_minisign_identity_proof,
     },
-    signatures::{PROOF_TYPE_ID_EIP191, PROOF_TYPE_ID_MINISIGN},
 };
 use crate::json_signatures::{
     create::{add_integrity_proof, IntegrityProof},
@@ -53,6 +52,7 @@ use crate::models::profiles::queries::{
 use crate::models::profiles::types::{
     IdentityProof,
     ProfileUpdateData,
+    ProofType,
 };
 use crate::models::relationships::queries::{
     create_follow_request,
@@ -389,7 +389,7 @@ async fn create_identity_proof(
                 &message,
                 &proof_data.signature,
             ).map_err(|_| ValidationError("invalid signature"))?;
-            PROOF_TYPE_ID_MINISIGN
+            ProofType::LegacyMinisignIdentityProof
         },
         Did::Pkh(ref did_pkh) => {
             if did_pkh.chain_id != ChainId::ethereum_mainnet() {
@@ -410,13 +410,13 @@ async fn create_identity_proof(
                 &message,
                 &proof_data.signature,
             ).map_err(|_| ValidationError("invalid signature"))?;
-            PROOF_TYPE_ID_EIP191
+            ProofType::LegacyEip191IdentityProof
         },
     };
 
     let proof = IdentityProof {
         issuer: did,
-        proof_type: proof_type.to_string(),
+        proof_type: proof_type,
         value: proof_data.signature.clone(),
     };
     let mut profile_data = ProfileUpdateData::from(&current_user.profile);
diff --git a/src/models/profiles/queries.rs b/src/models/profiles/queries.rs
index 02d405d..43dd07f 100644
--- a/src/models/profiles/queries.rs
+++ b/src/models/profiles/queries.rs
@@ -647,6 +647,7 @@ mod tests {
         ExtraField,
         IdentityProof,
         ProfileCreateData,
+        ProofType,
     };
     use crate::models::users::queries::create_user;
     use crate::models::users::types::UserCreateData;
@@ -794,7 +795,7 @@ mod tests {
         let db_client = &mut create_test_database().await;
         let identity_proof = IdentityProof {
             issuer: Did::Pkh(DidPkh::from_address(&ETHEREUM, "0x1234abcd")),
-            proof_type: "ethereum".to_string(),
+            proof_type: ProofType::LegacyEip191IdentityProof,
             value: "13590013185bdea963".to_string(),
         };
         let profile_data = ProfileCreateData {
diff --git a/src/models/profiles/types.rs b/src/models/profiles/types.rs
index 6617694..9a36652 100644
--- a/src/models/profiles/types.rs
+++ b/src/models/profiles/types.rs
@@ -1,4 +1,6 @@
 use std::convert::TryFrom;
+use std::fmt;
+use std::str::FromStr;
 
 use chrono::{DateTime, Duration, Utc};
 use postgres_types::FromSql;
@@ -14,7 +16,10 @@ use crate::activitypub::actors::types::{Actor, ActorAddress};
 use crate::activitypub::identifiers::local_actor_id;
 use crate::database::json_macro::{json_from_sql, json_to_sql};
 use crate::errors::{ConversionError, ValidationError};
-use crate::identity::did::Did;
+use crate::identity::{
+    did::Did,
+    signatures::{PROOF_TYPE_ID_EIP191, PROOF_TYPE_ID_MINISIGN},
+};
 use crate::utils::caip2::ChainId;
 use super::validators::{
     validate_username,
@@ -23,10 +28,56 @@ use super::validators::{
     clean_extra_fields,
 };
 
+#[derive(Clone, Debug)]
+pub enum ProofType {
+    LegacyEip191IdentityProof,
+    LegacyMinisignIdentityProof,
+}
+
+impl FromStr for ProofType {
+    type Err = ConversionError;
+
+    fn from_str(value: &str) -> Result<Self, Self::Err> {
+        let proof_type = match value {
+            PROOF_TYPE_ID_EIP191 => Self::LegacyEip191IdentityProof,
+            PROOF_TYPE_ID_MINISIGN => Self::LegacyMinisignIdentityProof,
+            _ => return Err(ConversionError),
+        };
+        Ok(proof_type)
+    }
+}
+
+impl fmt::Display for ProofType {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let proof_type_str = match self {
+            Self::LegacyEip191IdentityProof => PROOF_TYPE_ID_EIP191,
+            Self::LegacyMinisignIdentityProof => PROOF_TYPE_ID_MINISIGN,
+        };
+        write!(formatter, "{}", proof_type_str)
+    }
+}
+
+impl<'de> Deserialize<'de> for ProofType {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        String::deserialize(deserializer)?
+            .parse().map_err(DeserializerError::custom)
+    }
+}
+
+impl Serialize for ProofType {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.serialize_str(&self.to_string())
+    }
+}
+
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub struct IdentityProof {
     pub issuer: Did,
-    pub proof_type: String,
+    pub proof_type: ProofType,
     pub value: String,
 }