diff --git a/Source/Core/Core/IOS/ES/Formats.cpp b/Source/Core/Core/IOS/ES/Formats.cpp
index 66ebb0dff4..e0cc70dea3 100644
--- a/Source/Core/Core/IOS/ES/Formats.cpp
+++ b/Source/Core/Core/IOS/ES/Formats.cpp
@@ -307,8 +307,8 @@ std::vector<u8> TicketReader::GetRawTicketView(u32 ticket_num) const
 std::string TicketReader::GetIssuer() const
 {
   const char* bytes =
-      reinterpret_cast<const char*>(m_bytes.data() + offsetof(Ticket, signature_issuer));
-  return std::string(bytes, strnlen(bytes, sizeof(Ticket::signature_issuer)));
+      reinterpret_cast<const char*>(m_bytes.data() + offsetof(Ticket, signature.issuer));
+  return std::string(bytes, strnlen(bytes, sizeof(Ticket::signature.issuer)));
 }
 
 u32 TicketReader::GetDeviceId() const
diff --git a/Source/Core/Core/IOS/ES/Formats.h b/Source/Core/Core/IOS/ES/Formats.h
index 77db4ec3b3..178fc643fa 100644
--- a/Source/Core/Core/IOS/ES/Formats.h
+++ b/Source/Core/Core/IOS/ES/Formats.h
@@ -16,6 +16,7 @@
 
 #include "Common/CommonTypes.h"
 #include "Common/NandPaths.h"
+#include "Core/IOS/IOSC.h"
 #include "DiscIO/Enums.h"
 
 class PointerWrap;
@@ -56,10 +57,7 @@ enum TitleFlags : u32
 #pragma pack(push, 4)
 struct TMDHeader
 {
-  u32 signature_type;
-  u8 rsa_2048_signature[256];
-  u8 fill[60];
-  u8 issuer[64];
+  SignatureRSA2048 signature;
   u8 tmd_version;
   u8 ca_crl_version;
   u8 signer_crl_version;
@@ -120,10 +118,7 @@ static_assert(sizeof(TicketView) == 0xd8, "TicketView has the wrong size");
 // the only ticket type that is supported by the Wii's IOS.
 struct Ticket
 {
-  u32 signature_type;
-  u8 signature[256];
-  u8 unused[60];
-  u8 signature_issuer[0x40];
+  SignatureRSA2048 signature;
   u8 server_public_key[0x3c];
   u8 version;
   u8 ca_crl_version;
diff --git a/Source/Core/Core/IOS/IOSC.h b/Source/Core/Core/IOS/IOSC.h
index 773fba36c4..2c4c806c92 100644
--- a/Source/Core/Core/IOS/IOSC.h
+++ b/Source/Core/Core/IOS/IOSC.h
@@ -17,6 +17,85 @@ class PointerWrap;
 
 namespace IOS
 {
+enum class SignatureType : u32
+{
+  RSA4096 = 0x00010000,
+  RSA2048 = 0x00010001,
+  // XXX: Add support for ECC (0x00010002).
+};
+
+enum class PublicKeyType : u32
+{
+  RSA4096 = 0,
+  RSA2048 = 1,
+};
+
+#pragma pack(push, 4)
+struct SignatureRSA4096
+{
+  SignatureType type;
+  u8 sig[0x200];
+  u8 fill[0x3c];
+  char issuer[0x40];
+};
+static_assert(sizeof(SignatureRSA4096) == 0x280, "Wrong size for SignatureRSA4096");
+
+struct SignatureRSA2048
+{
+  SignatureType type;
+  u8 sig[0x100];
+  u8 fill[0x3c];
+  char issuer[0x40];
+};
+static_assert(sizeof(SignatureRSA2048) == 0x180, "Wrong size for SignatureRSA2048");
+
+struct SignatureECC
+{
+  SignatureType type;
+  u8 sig[0x3c];
+  u8 fill[0x40];
+  char issuer[0x40];
+};
+static_assert(sizeof(SignatureECC) == 0xc0, "Wrong size for SignatureECC");
+
+// Source: https://wiibrew.org/wiki/Certificate_chain
+struct CertHeader
+{
+  PublicKeyType public_key_type;
+  char name[0x40];
+  u32 id;
+};
+
+struct CertRSA4096
+{
+  SignatureRSA4096 signature;
+  CertHeader header;
+  // The signature is RSA4096, but the key is a RSA2048 public key,
+  // so its size is 0x100, not 0x200, as one would expect from the name.
+  u8 public_key[0x100];
+  u8 exponent[0x4];
+  u8 pad[0x34];
+};
+static_assert(sizeof(CertRSA4096) == 0x400, "Wrong size for CertRSA4096");
+
+struct CertRSA2048
+{
+  SignatureRSA2048 signature;
+  CertHeader header;
+  u8 public_key[0x100];
+  u8 exponent[0x4];
+  u8 pad[0x34];
+};
+static_assert(sizeof(CertRSA2048) == 0x300, "Wrong size for CertRSA2048");
+
+union Cert
+{
+  SignatureType type;
+  CertRSA4096 rsa4096;
+  CertRSA2048 rsa2048;
+};
+#pragma pack(pop)
+
 namespace HLE
 {
 enum ReturnCode : s32;