diff --git a/card-functionality/src/tests.rs b/card-functionality/src/tests.rs
index c9a5a2d..df16fab 100644
--- a/card-functionality/src/tests.rs
+++ b/card-functionality/src/tests.rs
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
 use anyhow::Result;
+use std::convert::TryFrom;
 use std::str::FromStr;
 use std::string::FromUtf8Error;
 use thiserror;
@@ -229,7 +230,7 @@ pub fn test_keygen(
     // Generate all three subkeys on card
     let algo = param[0];
 
-    let alg = AlgoSimple::from(algo);
+    let alg = AlgoSimple::try_from(algo)?;
 
     println!(" Generate subkey for Signing");
     let (pkm, ts) =
diff --git a/openpgp-card/src/algorithm.rs b/openpgp-card/src/algorithm.rs
index e2f0c70..c50ef7c 100644
--- a/openpgp-card/src/algorithm.rs
+++ b/openpgp-card/src/algorithm.rs
@@ -36,11 +36,13 @@ pub enum AlgoSimple {
     Curve25519,
 }
 
-impl From<&str> for AlgoSimple {
-    fn from(algo: &str) -> Self {
+impl TryFrom<&str> for AlgoSimple {
+    type Error = anyhow::Error;
+
+    fn try_from(algo: &str) -> Result<Self, anyhow::Error> {
         use AlgoSimple::*;
 
-        match algo {
+        Ok(match algo {
             "RSA1k/17" => RSA1k(17),
             "RSA1k/32" => RSA1k(32),
             "RSA2k/17" => RSA2k(17),
@@ -53,8 +55,8 @@ impl From<&str> for AlgoSimple {
             "NIST384" => NIST384,
             "NIST521" => NIST521,
             "Curve25519" => Curve25519,
-            _ => panic!("unexpected algo {}", algo),
-        }
+            _ => return Err(anyhow!("unexpected algo {}", algo)),
+        })
     }
 }
 
diff --git a/openpgp-card/src/crypto_data.rs b/openpgp-card/src/crypto_data.rs
index 95f78ac..f1efce7 100644
--- a/openpgp-card/src/crypto_data.rs
+++ b/openpgp-card/src/crypto_data.rs
@@ -22,6 +22,8 @@ pub enum Hash<'a> {
 }
 
 impl Hash<'_> {
+    /// This fn is currently only used in the context of creating a
+    /// digestinfo for SHA*. Other OIDs are not implemented.
     pub(crate) fn oid(&self) -> Option<&'static [u8]> {
         match self {
             Self::SHA256(_) => {
@@ -33,8 +35,8 @@ impl Hash<'_> {
             Self::SHA512(_) => {
                 Some(&[0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03])
             }
-            Self::EdDSA(_) => panic!("This should not be called"),
-            Self::ECDSA(_) => panic!("This should not be called"),
+            Self::EdDSA(_) => panic!("OIDs for EdDSA are unimplemented"),
+            Self::ECDSA(_) => panic!("OIDs for ECDSA are unimplemented"),
         }
     }
 
diff --git a/tools/src/bin/opgpcard/main.rs b/tools/src/bin/opgpcard/main.rs
index c1f4082..ed8f3b4 100644
--- a/tools/src/bin/opgpcard/main.rs
+++ b/tools/src/bin/opgpcard/main.rs
@@ -464,7 +464,7 @@ fn generate_keys(
         Some("nistp384") => vec![AlgoSimple::NIST384],
         Some("nistp521") => vec![AlgoSimple::NIST521],
         Some("25519") => vec![AlgoSimple::Curve25519],
-        _ => unimplemented!("unexpected algorithm"),
+        _ => return Err(anyhow!("Unexpected algorithm")),
     };
 
     log::info!(