diff --git a/lib/help/node_alg.js b/lib/help/node_alg.js
new file mode 100644
index 00000000..f5b95ee2
--- /dev/null
+++ b/lib/help/node_alg.js
@@ -0,0 +1,19 @@
+module.exports = (alg) => {
+  switch (alg) {
+    case 'RS256':
+    case 'PS256':
+    case 'HS256':
+    case 'ES256':
+      return 'sha256'
+    case 'RS384':
+    case 'PS384':
+    case 'HS384':
+    case 'ES384':
+      return 'sha384'
+    case 'RS512':
+    case 'PS512':
+    case 'HS512':
+    case 'ES512':
+      return 'sha512'
+  }
+}
diff --git a/lib/jwa/ecdsa.js b/lib/jwa/ecdsa.js
index 7f451592..80df4b2c 100644
--- a/lib/jwa/ecdsa.js
+++ b/lib/jwa/ecdsa.js
@@ -3,17 +3,7 @@ const { createSign, createVerify } = require('crypto')
 
 const { derToJose, joseToDer } = require('../help/ecdsa_signatures')
 const { KEYOBJECT } = require('../help/symbols')
-
-const resolveNodeAlg = (alg) => {
-  switch (alg) {
-    case 'ES256':
-      return 'RSA-SHA256'
-    case 'ES384':
-      return 'RSA-SHA384'
-    case 'ES512':
-      return 'RSA-SHA512'
-  }
-}
+const resolveNodeAlg = require('../help/node_alg')
 
 const sign = (jwaAlg, nodeAlg, { [KEYOBJECT]: keyObject }, payload) => {
   const sign = createSign(nodeAlg)
diff --git a/lib/jwa/hmac.js b/lib/jwa/hmac.js
index dc6e54c2..f4aab782 100644
--- a/lib/jwa/hmac.js
+++ b/lib/jwa/hmac.js
@@ -3,17 +3,7 @@ const { createHmac } = require('crypto')
 
 const { KEYOBJECT } = require('../help/symbols')
 const timingSafeEqual = require('../help/timing_safe_equal')
-
-const resolveHmacAlg = (alg) => {
-  switch (alg) {
-    case 'HS256':
-      return 'sha256'
-    case 'HS384':
-      return 'sha384'
-    case 'HS512':
-      return 'sha512'
-  }
-}
+const resolveNodeAlg = require('../help/node_alg')
 
 const sign = (jwaAlg, hmacAlg, { [KEYOBJECT]: keyObject }, payload) => {
   const hmac = createHmac(hmacAlg, keyObject)
@@ -32,7 +22,7 @@ const verify = (jwaAlg, hmacAlg, { [KEYOBJECT]: keyObject }, payload, signature)
 
 module.exports = (JWA) => {
   ['HS256', 'HS384', 'HS512'].forEach((jwaAlg) => {
-    const hmacAlg = resolveHmacAlg(jwaAlg)
+    const hmacAlg = resolveNodeAlg(jwaAlg)
 
     assert(!JWA.sign.has(jwaAlg), `sign alg ${jwaAlg} already registered`)
     assert(!JWA.verify.has(jwaAlg), `verify alg ${jwaAlg} already registered`)
diff --git a/lib/jwa/rsassa.js b/lib/jwa/rsassa.js
index 92655e5f..5dcda324 100644
--- a/lib/jwa/rsassa.js
+++ b/lib/jwa/rsassa.js
@@ -2,17 +2,7 @@ const { strict: assert } = require('assert')
 const { createSign, createVerify } = require('crypto')
 
 const { KEYOBJECT } = require('../help/symbols')
-
-const resolveNodeAlg = (alg) => {
-  switch (alg) {
-    case 'RS256':
-      return 'RSA-SHA256'
-    case 'RS384':
-      return 'RSA-SHA384'
-    case 'RS512':
-      return 'RSA-SHA512'
-  }
-}
+const resolveNodeAlg = require('../help/node_alg')
 
 const sign = (nodeAlg, { [KEYOBJECT]: keyObject }, payload) => {
   const sign = createSign(nodeAlg)
diff --git a/lib/jwa/rsassa_pss.js b/lib/jwa/rsassa_pss.js
index a3d2fb68..7e141ce1 100644
--- a/lib/jwa/rsassa_pss.js
+++ b/lib/jwa/rsassa_pss.js
@@ -2,17 +2,7 @@ const { strict: assert } = require('assert')
 const { createSign, createVerify, constants } = require('crypto')
 
 const { KEYOBJECT } = require('../help/symbols')
-
-const resolveNodeAlg = (alg) => {
-  switch (alg) {
-    case 'PS256':
-      return 'RSA-SHA256'
-    case 'PS384':
-      return 'RSA-SHA384'
-    case 'PS512':
-      return 'RSA-SHA512'
-  }
-}
+const resolveNodeAlg = require('../help/node_alg')
 
 const sign = (nodeAlg, { [KEYOBJECT]: keyObject, length }, payload) => {
   const sign = createSign(nodeAlg)