diff --git a/libs/apkverify/src/algorithms.rs b/libs/apkverify/src/algorithms.rs
index edfa946..9e6c415 100644
--- a/libs/apkverify/src/algorithms.rs
+++ b/libs/apkverify/src/algorithms.rs
@@ -17,7 +17,7 @@
 //! Algorithms used for APK Signature Scheme.
 
 use anyhow::{ensure, Result};
-use num_derive::FromPrimitive;
+use num_derive::{FromPrimitive, ToPrimitive};
 use openssl::hash::MessageDigest;
 use openssl::pkey::{self, PKey};
 use openssl::rsa::Padding;
@@ -25,23 +25,58 @@
 use std::cmp::Ordering;
 
 /// [Signature Algorithm IDs]: https://source.android.com/docs/security/apksigning/v2#signature-algorithm-ids
+/// [SignatureAlgorithm.java]: (tools/apksig/src/main/java/com/android/apksig/internal/apk/SignatureAlgorithm.java)
 ///
 /// Some of the algorithms are not implemented. See b/197052981.
-#[derive(Clone, Debug, Eq, FromPrimitive)]
+#[derive(Clone, Debug, Eq, FromPrimitive, ToPrimitive)]
 #[repr(u32)]
 pub enum SignatureAlgorithmID {
+    /// RSASSA-PSS with SHA2-256 digest, SHA2-256 MGF1, 32 bytes of salt, trailer: 0xbc, content
+    /// digested using SHA2-256 in 1 MB chunks.
     RsaPssWithSha256 = 0x0101,
+
+    /// RSASSA-PSS with SHA2-512 digest, SHA2-512 MGF1, 64 bytes of salt, trailer: 0xbc, content
+    /// digested using SHA2-512 in 1 MB chunks.
     RsaPssWithSha512 = 0x0102,
+
+    /// RSASSA-PKCS1-v1_5 with SHA2-256 digest, content digested using SHA2-256 in 1 MB chunks.
     RsaPkcs1V15WithSha256 = 0x0103,
+
+    /// RSASSA-PKCS1-v1_5 with SHA2-512 digest, content digested using SHA2-512 in 1 MB chunks.
     RsaPkcs1V15WithSha512 = 0x0104,
+
+    /// ECDSA with SHA2-256 digest, content digested using SHA2-256 in 1 MB chunks.
     EcdsaWithSha256 = 0x0201,
+
+    /// ECDSA with SHA2-512 digest, content digested using SHA2-512 in 1 MB chunks.
     EcdsaWithSha512 = 0x0202,
+
+    /// DSA with SHA2-256 digest, content digested using SHA2-256 in 1 MB chunks.
+    /// Signing is done deterministically according to RFC 6979.
     DsaWithSha256 = 0x0301,
+
+    /// RSASSA-PKCS1-v1_5 with SHA2-256 digest, content digested using SHA2-256 in 4 KB
+    /// chunks, in the same way fsverity operates. This digest and the content length
+    /// (before digestion, 8 bytes in little endian) construct the final digest.
     VerityRsaPkcs1V15WithSha256 = 0x0421,
+
+    /// ECDSA with SHA2-256 digest, content digested using SHA2-256 in 4 KB chunks, in the
+    /// same way fsverity operates. This digest and the content length (before digestion,
+    /// 8 bytes in little endian) construct the final digest.
     VerityEcdsaWithSha256 = 0x0423,
+
+    /// DSA with SHA2-256 digest, content digested using SHA2-256 in 4 KB chunks, in the
+    /// same way fsverity operates. This digest and the content length (before digestion,
+    /// 8 bytes in little endian) construct the final digest.
     VerityDsaWithSha256 = 0x0425,
 }
 
+impl Default for SignatureAlgorithmID {
+    fn default() -> Self {
+        SignatureAlgorithmID::DsaWithSha256
+    }
+}
+
 impl Ord for SignatureAlgorithmID {
     /// Ranks the signature algorithm according to the corresponding content
     /// digest algorithm's rank.
diff --git a/libs/apkverify/src/lib.rs b/libs/apkverify/src/lib.rs
index 040c304..084a910 100644
--- a/libs/apkverify/src/lib.rs
+++ b/libs/apkverify/src/lib.rs
@@ -25,4 +25,5 @@
 mod ziputil;
 
 // TODO(b/197052981) fallback to v2 when v3 not found
+pub use algorithms::SignatureAlgorithmID;
 pub use v3::{get_public_key_der, pick_v4_apk_digest, verify};
diff --git a/libs/idsig/src/apksigv4.rs b/libs/idsig/src/apksigv4.rs
index f8ca184..92f8963 100644
--- a/libs/idsig/src/apksigv4.rs
+++ b/libs/idsig/src/apksigv4.rs
@@ -15,7 +15,7 @@
  */
 
 use anyhow::{anyhow, bail, Context, Result};
-use apkverify::pick_v4_apk_digest;
+use apkverify::{pick_v4_apk_digest, SignatureAlgorithmID};
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
 use num_derive::{FromPrimitive, ToPrimitive};
 use num_traits::{FromPrimitive, ToPrimitive};
@@ -69,7 +69,7 @@
     /// Public key of the signer in ASN.1 DER form. This must match the `x509_certificate` field.
     pub public_key: Box<[u8]>,
     /// Signature algorithm used to sign this file.
-    pub signature_algorithm_id: SignatureAlgorithmId,
+    pub signature_algorithm_id: SignatureAlgorithmID,
     /// The signature of this file.
     pub signature: Box<[u8]>,
 }
@@ -114,40 +114,6 @@
     }
 }
 
-/// Signature algorithm that can be used for idsig file
-#[derive(Debug, PartialEq, Eq, FromPrimitive, ToPrimitive)]
-#[allow(non_camel_case_types)]
-#[repr(u32)]
-pub enum SignatureAlgorithmId {
-    /// RSASSA-PSS with SHA2-256 digest, SHA2-256 MGF1, 32 bytes of salt, trailer: 0xbc
-    RSASSA_PSS_SHA2_256 = 0x0101,
-    /// RSASSA-PSS with SHA2-512 digest, SHA2-512 MGF1, 64 bytes of salt, trailer: 0xbc
-    RSASSA_PSS_SHA2_512 = 0x0102,
-    /// RSASSA-PKCS1-v1_5 with SHA2-256 digest.
-    RSASSA_PKCS1_SHA2_256 = 0x0103,
-    /// RSASSA-PKCS1-v1_5 with SHA2-512 digest.
-    RSASSA_PKCS1_SHA2_512 = 0x0104,
-    /// ECDSA with SHA2-256 digest.
-    ECDSA_SHA2_256 = 0x0201,
-    /// ECDSA with SHA2-512 digest.
-    ECDSA_SHA2_512 = 0x0202,
-    /// DSA with SHA2-256 digest
-    DSA_SHA2_256 = 0x0301,
-}
-
-impl SignatureAlgorithmId {
-    fn from(val: u32) -> Result<SignatureAlgorithmId> {
-        Self::from_u32(val)
-            .with_context(|| format!("{:#06x} is an unsupported signature algorithm", val))
-    }
-}
-
-impl Default for SignatureAlgorithmId {
-    fn default() -> Self {
-        SignatureAlgorithmId::DSA_SHA2_256
-    }
-}
-
 impl<R: Read + Seek> V4Signature<R> {
     /// Consumes a stream for an idsig file into a `V4Signature` struct.
     pub fn from(mut r: R) -> Result<V4Signature<R>> {
@@ -193,8 +159,11 @@
 
         apk.seek(SeekFrom::Start(start))?;
         let (signature_algorithm_id, apk_digest) = pick_v4_apk_digest(apk)?;
+        // TODO(b/246254355): Removes this conversion once pick_v4_apk_digest
+        // returns the enum SignatureAlgorithmID instead of raw integer.
         ret.signing_info.signature_algorithm_id =
-            SignatureAlgorithmId::from(signature_algorithm_id)?;
+            SignatureAlgorithmID::from_u32(signature_algorithm_id)
+                .context("Unsupported algorithm")?;
         ret.signing_info.apk_digest = apk_digest;
         // TODO(jiyong): add a signature to the signing_info struct
 
@@ -276,7 +245,8 @@
             x509_certificate: read_sized_array(&mut r)?,
             additional_data: read_sized_array(&mut r)?,
             public_key: read_sized_array(&mut r)?,
-            signature_algorithm_id: SignatureAlgorithmId::from(r.read_u32::<LittleEndian>()?)?,
+            signature_algorithm_id: SignatureAlgorithmID::from_u32(r.read_u32::<LittleEndian>()?)
+                .context("Unsupported signature algorithm")?,
             signature: read_sized_array(&mut r)?,
         })
     }
@@ -358,7 +328,7 @@
                    a8585c38d7f654835eb219ae9e176b44e86dcb23153e3d9d6",
             hexstring_from(si.signature.as_ref())
         );
-        assert_eq!(SignatureAlgorithmId::DSA_SHA2_256, si.signature_algorithm_id);
+        assert_eq!(SignatureAlgorithmID::DsaWithSha256, si.signature_algorithm_id);
 
         assert_eq!(36864, parsed.merkle_tree_size);
         assert_eq!(2251, parsed.merkle_tree_offset);