diff --git a/src/include/taler_extensions.h b/src/include/taler_extensions.h
index 0ef69a78d..1ef97b2e9 100644
--- a/src/include/taler_extensions.h
+++ b/src/include/taler_extensions.h
@@ -1,18 +1,18 @@
 /*
-  This file is part of TALER
-  Copyright (C) 2014-2021 Taler Systems SA
+   This file is part of TALER
+   Copyright (C) 2014-2021 Taler Systems SA
 
-  TALER is free software; you can redistribute it and/or modify it under the
-  terms of the GNU General Public License as published by the Free Software
-  Foundation; either version 3, or (at your option) any later version.
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
 
-  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 
-  You should have received a copy of the GNU General Public License along with
-  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
-*/
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
 /**
  * @file include/taler_extensions.h
  * @brief Interface for extensions
@@ -21,14 +21,51 @@
 #ifndef TALER_EXTENSIONS_H
 #define TALER_EXTENSIONS_H
 
+#include <gnunet/gnunet_util_lib.h>
+
+
+#define TALER_EXTENSION_SECTION_PREFIX "exchange-extension-"
+
+enum TALER_EXTENSION_ReturnValue
+{
+  TALER_EXTENSION_OK = 0,
+  TALER_EXTENSION_ERROR_PARSING = 1,
+  TALER_EXTENSION_ERROR_INVALID = 2,
+  TALER_EXTENSION_ERROR_SYS = 3
+};
+
+
+/*
+ * TALER Age Restriction Extensions
+ */
+
+#define TALER_EXTENSION_SECTION_AGE_RESTRICTION TALER_EXTENSION_SECTION_PREFIX \
+  "agerestriction"
+
+/**
+ * The default age mask represents the age groups
+ * 0-7, 8-9, 10-11, 12-13, 14-15, 16-17, 18-20, 21-...
+ */
+#define TALER_EXTENSION_DEFAULT_AGE_MASK (1 | 1 << 8 | 1 << 10 | 1 << 12 | 1 << \
+                                          14 | 1 << 16 | 1 << 18 | 1 << 21)
+
+/**
+ * @param groups String representation of age groups, like: "8:10:12:14:16:18:21"
+ * @param[out] mask Mask representation for age restriction.
+ * @return Error, if age groups were invalid, OK otherwise.
+ */
+enum TALER_EXTENSION_ReturnValue
+TALER_parse_age_group_string (char *groups,
+                              struct TALER_AgeMask *mask);
+
 /**
  *
  * @param cfg
- * @param[out] mask for age restriction
+ * @param[out] mask for age restriction, will be set to 0 if age restriction is disabled.
  * @return Error if extension for age restriction was set but age groups were
  *         invalid, OK otherwise.
  */
-enum GNUNET_GenericReturnValue
+enum TALER_EXTENSION_ReturnValue
 TALER_get_age_mask (const struct GNUNET_CONFIGURATION_Handle *cfg,
                     struct TALER_AgeMask *mask);
 
diff --git a/src/util/extension_age_restriction.c b/src/util/extension_age_restriction.c
index dbb4f3e23..6bbfde04c 100644
--- a/src/util/extension_age_restriction.c
+++ b/src/util/extension_age_restriction.c
@@ -1,18 +1,18 @@
 /*
-  This file is part of TALER
-  Copyright (C) 2014-2020 Taler Systems SA
+   This file is part of TALER
+   Copyright (C) 2014-2020 Taler Systems SA
 
-  TALER is free software; you can redistribute it and/or modify it under the
-  terms of the GNU General Public License as published by the Free Software
-  Foundation; either version 3, or (at your option) any later version.
+   TALER is free software; you can redistribute it and/or modify it under the
+   terms of the GNU General Public License as published by the Free Software
+   Foundation; either version 3, or (at your option) any later version.
 
-  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 
-  You should have received a copy of the GNU General Public License along with
-  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
-*/
+   You should have received a copy of the GNU General Public License along with
+   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
 /**
  * @file extension_age_restriction.c
  * @brief Utility functions regarding age restriction
@@ -20,29 +20,160 @@
  */
 #include "platform.h"
 #include "taler_util.h"
+#include "taler_extensions.h"
+#include "stdint.h"
 
 
 /**
  *
- * @param cfg
- * @param[out] mask for age restriction
- * @return Error if extension for age restriction was set but age groups were
+ * @param cfg Handle to the GNUNET configuration
+ * @param[out] Mask for age restriction. Will be 0 if age restriction was not enabled in the config.
+ * @return Error if extension for age restriction was set, but age groups were
  *         invalid, OK otherwise.
  */
-enum GNUNET_GenericReturnValue
+enum TALER_EXTENSION_ReturnValue
 TALER_get_age_mask (const struct GNUNET_CONFIGURATION_Handle *cfg,
                     struct TALER_AgeMask *mask)
 {
-  /* FIXME-Oec:
-   *
-   * - Detect if age restriction is enabled in config
-   * - if not, return 0 mask
-   * - else, parse age group and serialize into mask
-   * - return Error on
-   *
-   * */
-  mask->mask = 0;
-  return GNUNET_OK;
+  char *groups;
+  enum TALER_EXTENSION_ReturnValue ret = TALER_EXTENSION_ERROR_SYS;
+
+  if ((GNUNET_NO == GNUNET_CONFIGURATION_have_value (cfg,
+                                                     TALER_EXTENSION_SECTION_AGE_RESTRICTION,
+                                                     "ENABLED")) ||
+      (GNUNET_NO == GNUNET_CONFIGURATION_get_value_yesno (cfg,
+                                                          TALER_EXTENSION_SECTION_AGE_RESTRICTION,
+                                                          "ENABLED")))
+  {
+    /* Age restriction is not enabled */
+    mask->mask = 0;
+    return TALER_EXTENSION_OK;
+  }
+
+  /* Age restriction is enabled, extract age groups */
+  if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_string (cfg,
+                                                          TALER_EXTENSION_SECTION_AGE_RESTRICTION,
+                                                          "AGE_GROUPS",
+                                                          &groups))
+  {
+    /* FIXME: log error? */
+    return TALER_EXTENSION_ERROR_SYS;
+  }
+  if (groups == NULL)
+  {
+    /* No groups defined in config, return default_age_mask */
+    mask->mask = TALER_EXTENSION_DEFAULT_AGE_MASK;
+    return TALER_EXTENSION_OK;
+  }
+
+  ret = TALER_parse_age_group_string (groups, mask);
+  GNUNET_free (groups);
+  return ret;
+}
+
+
+/**
+ * @param groups String representation of the age groups. Must be of the form
+ *  a:b:...:n:m
+ * with
+ *  0 < a < b <...< n < m < 32
+ * @param[out] mask Bit representation of the age groups.
+ * @return Error if string was invalid, OK otherwise.
+ */
+enum TALER_EXTENSION_ReturnValue
+TALER_parse_age_group_string (char *groups,
+                              struct TALER_AgeMask *mask)
+{
+  enum TALER_EXTENSION_ReturnValue ret = TALER_EXTENSION_ERROR_SYS;
+  char *pos;
+  int prev = -1;
+  unsigned int val;
+  char dummy;
+
+  while (1)
+  {
+    pos = strchr (groups, ':');
+    if (NULL != pos)
+    {
+      *pos = 0;
+    }
+
+    if (1 != sscanf (groups,
+                     "%u%c",
+                     &val,
+                     &dummy))
+    {
+      /* Invalid input */
+      mask->mask = 0;
+      ret = TALER_EXTENSION_ERROR_PARSING;
+      break;
+    }
+    else if ((0 >= val) || (32 <= val) || (prev >= val))
+    {
+      /* Invalid value */
+      mask->mask = 0;
+      ret = TALER_EXTENSION_ERROR_INVALID;
+      break;
+    }
+
+    /* Set the corresponding bit in the mask */
+    mask->mask |= 1 << val;
+
+    if (NULL == pos)
+    {
+      /* We reached the end. Mark zeroth age-group and exit. */
+      mask->mask |= 1;
+      ret = TALER_EXTENSION_OK;
+      break;
+    }
+
+    prev = val;
+    groups = pos + 1;
+  }
+
+  return ret;
+}
+
+
+/**
+ * @param mask Age mask
+ * @return String representation of the age mask, allocated by GNUNET_malloc.
+ *         Can be used as value in the TALER config.
+ */
+char *
+TALER_age_mask_to_string (struct TALER_AgeMask *m)
+{
+  uint32_t mask = m->mask;
+  unsigned int n = 0;
+  char *buf = GNUNET_malloc (32 * 3); // max characters possible
+  char *pos = buf;
+
+  if (NULL == buf)
+  {
+    return buf;
+  }
+
+  while (mask != 0)
+  {
+    mask >>= 1;
+    n++;
+    if (0 == (mask & 1))
+    {
+      continue;
+    }
+
+    if (n > 9)
+    {
+      *(pos++) = '0' + n / 10;
+    }
+    *(pos++) = '0' + n % 10;
+
+    if (0 != (mask >> 1))
+    {
+      *(pos++) = ':';
+    }
+  }
+  return buf;
 }