diff --git a/__pycache__/verify_nzb.cpython-312.pyc b/__pycache__/verify_nzb.cpython-312.pyc
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diff --git a/tests/__pycache__/__init__.cpython-312.pyc b/tests/__pycache__/__init__.cpython-312.pyc
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diff --git a/tests/__pycache__/test_verify_nzb.cpython-312.pyc b/tests/__pycache__/test_verify_nzb.cpython-312.pyc
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diff --git a/verify_nzb.py b/verify_nzb.py
index 953dccd..629fc9a 100644
--- a/verify_nzb.py
+++ b/verify_nzb.py
@@ -115,20 +115,26 @@ def _parse_yenc_attrs(line: bytes) -> dict[str, str]:
     return attrs
 
 
+_YENC_TRANSLATE_TABLE = bytes((i - 42) % 256 for i in range(256))
+
 def _decode_yenc_lines(lines: Iterable[bytes]) -> bytes:
     decoded = bytearray()
     for line in lines:
-        index = 0
-        while index < len(line):
-            byte = line[index]
-            if byte == 61:
-                index += 1
-                if index >= len(line):
-                    raise ValueError("dangling yEnc escape")
-                byte = (line[index] - 64) % 256
-            decoded.append((byte - 42) % 256)
-            index += 1
-    return bytes(decoded)
+        # Process escapes on a per-line basis
+        start = 0
+        while True:
+            pos = line.find(b'=', start)
+            if pos == -1:
+                decoded.extend(line[start:])
+                break
+            decoded.extend(line[start:pos])
+            if pos + 1 >= len(line):
+                raise ValueError("dangling yEnc escape")
+            decoded.append((line[pos + 1] - 64) % 256)
+            start = pos + 2
+
+    # Utilize C-backed built-in methods for significant performance gain
+    return bytes(decoded.translate(_YENC_TRANSLATE_TABLE))
 
 
 def validate_yenc_body(lines: Iterable[bytes | str]) -> YencValidationResult: