diff --git a/biostools/extractors.py b/biostools/extractors.py
index 5f85ea8..9b3988c 100644
--- a/biostools/extractors.py
+++ b/biostools/extractors.py
@@ -1634,7 +1634,6 @@ class InterleaveExtractor(Extractor):
 
 		# Write all deinterleaved permutations, as some sets may
 		# contain the same interleaved string on more than one part.
-		alphanumeric = '0123456789abcdefghijklmn'
 		file_counter = 0
 		part_count = len(data)
 		buf = bytearray(part_size * part_count)
@@ -1646,7 +1645,7 @@ class InterleaveExtractor(Extractor):
 				data_offset += 1
 
 			# Write deinterleaved file.
-			f = open(os.path.join(dest_dir, 'deinterleaved_' + alphanumeric[file_counter] + '.bin'), 'wb')
+			f = open(os.path.join(dest_dir, 'deinterleaved_' + ''.join(util.base62[data_index] for data_index in permutation) + '.bin'), 'wb')
 			f.write(buf)
 			f.close()
 			file_counter += 1
@@ -1661,7 +1660,7 @@ class InterleaveExtractor(Extractor):
 		for counterpart_path in counterpart_paths:
 			# Move original file.
 			try:
-				shutil.move(counterpart_path, os.path.join(dest_dir, 'interleaved_' + alphanumeric[file_counter] + '.bin'))
+				shutil.move(counterpart_path, os.path.join(dest_dir, 'interleaved_' + util.base62[file_counter] + '.bin'))
 			except:
 				pass
 			file_counter += 1
@@ -1751,6 +1750,7 @@ class OMFExtractor(Extractor):
 				while data:
 					data = in_f.read(1048576)
 					out_f.write(data)
+
 				out_f.close()
 			except:
 				in_f.close()
@@ -2215,7 +2215,7 @@ class VMExtractor(ArchiveExtractor):
 		floppy_media = 'floppy.144'
 
 		# Copy original file and blank floppy image to the destination directory.
-		exe_name = util.random_name(8, alnum_only=True).lower() + '.exe'
+		exe_name = util.random_name(8, charset=util.random_name_nosymbols).lower() + '.exe'
 		exe_path = os.path.join(dest_dir, exe_name)
 		image_path = os.path.join(dest_dir, util.random_name(8) + '.img')
 		try:
@@ -2301,7 +2301,7 @@ class VMExtractor(ArchiveExtractor):
 				# Create filename for the individual ETI.
 				eti_name = temp_files[0] # dummy
 				while eti_name in temp_files:
-					eti_name = util.random_name(8, alnum_only=True).lower() + '.eti'
+					eti_name = util.random_name(8, charset=util.random_name_nosymbols).lower() + '.eti'
 				temp_files.append(eti_name)
 
 				# Sanitize extracted filename to not overwrite ourselves.
@@ -2361,7 +2361,7 @@ class VMExtractor(ArchiveExtractor):
 		   required for Siemens Nixdorf FastPacket with its LZEXE-compressed stub."""
 
 		# Copy original file to the destination directory.
-		exe_name = util.random_name(8, alnum_only=True).lower() + '.exe'
+		exe_name = util.random_name(8, charset=util.random_name_nosymbols).lower() + '.exe'
 		exe_path = os.path.join(dest_dir, exe_name)
 		try:
 			shutil.copy2(file_path, exe_path)
@@ -2369,7 +2369,7 @@ class VMExtractor(ArchiveExtractor):
 			return True
 
 		# Generate a name for the unpacked file.
-		unpacked_name = util.random_name(8, alnum_only=True).lower() + '.ulz'
+		unpacked_name = util.random_name(8, charset=util.random_name_nosymbols).lower() + '.ulz'
 		unpacked_path = os.path.join(dest_dir, unpacked_name)
 
 		# Create batch file for extraction.
diff --git a/biostools/util.py b/biostools/util.py
index b4345d4..7034b16 100644
--- a/biostools/util.py
+++ b/biostools/util.py
@@ -21,6 +21,14 @@ from biostools.pciutil import *
 date_pattern_mmddyy = re.compile('''(?P<month>[0-9]{2})/(?P<day>[0-9]{2})/(?P<year>[0-9]{2,4})''')
 number_pattern = re.compile('''[0-9]+''')
 
+digits = '0123456789'
+lowercase = 'abcdefghijklmnopqrstuvwxyz'
+uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+fn_symbols = '$%\'-_@~`!(){}^#&.+,;=[]'
+base62 = digits + lowercase + uppercase
+random_name_symbols = lowercase + digits + fn_symbols + uppercase
+random_name_nosymbols = lowercase + digits + uppercase
+
 _error_log_lock = multiprocessing.Lock()
 
 
@@ -158,14 +166,9 @@ def log_traceback(*args):
 		traceback.print_exc(file=f)
 		f.close()
 
-def random_name(chars=16, alnum_only=False):
-	"""Generate a random filename using valid DOS/Windows characters
-	   (alnum_only=False) or alphanumeric characters (alnum_only=True)."""
-	if alnum_only:
-		symbols = ''
-	else:
-		symbols = '$%\'-_@~`!(){}^#&.+,;=[]'
-	return ''.join(random.choice('abcdefghijklmnopqrstuvwxyz0123456789' + symbols + 'ABCDEFGHIJKLMNOPQRSTUVWXYZ') for x in range(chars))
+def random_name(chars=16, charset=random_name_symbols):
+	"""Generate a random filename using the given charset."""
+	return ''.join(random.choice(charset) for x in range(chars))
 
 def read_complement(file_path, file_header=None, max_size=16777216):
 	"""Read up to max_size from file_path starting at the end of file_header.