diff --git a/exosphere/src/interrupt.c b/exosphere/src/interrupt.c
index ff5af5ebe..7f79b20f0 100644
--- a/exosphere/src/interrupt.c
+++ b/exosphere/src/interrupt.c
@@ -11,8 +11,7 @@ static struct {
 } g_registered_interrupts[MAX_REGISTERED_INTERRUPTS] = { {0, NULL}, {0, NULL}, {0, NULL}, {0, NULL} };
 
 static unsigned int get_interrupt_id(void) {
-    return 0;
-    /* TODO */
+    return GICC_IAR;
 }
 
 /* Initializes the GIC. TODO: This must be called during wakeup. */
diff --git a/exosphere/src/lp0.c b/exosphere/src/lp0.c
index 83690ee22..f3e1d2198 100644
--- a/exosphere/src/lp0.c
+++ b/exosphere/src/lp0.c
@@ -22,8 +22,55 @@ extern const uint32_t bpmpfw_bin_size;
 
 /* Save security engine, and go to sleep. */
 void save_se_and_power_down_cpu(void) {
+    uint32_t tzram_cmac[0x4] = {0};
+    
+    uint8_t *tzram_encryption_src = (uint8_t *)(LP0_ENTRY_GET_RAM_SEGMENT_ADDRESS(LP0_ENTRY_RAM_SEGMENT_ID_ENCRYPTED_TZRAM));
+    uint8_t *tzram_encryption_dst = (uint8_t *)(LP0_ENTRY_GET_RAM_SEGMENT_ADDRESS(LP0_ENTRY_RAM_SEGMENT_ID_CURRENT_TZRAM));
+    uint8_t *tzram_store_address = (uint8_t *)(WARMBOOT_GET_RAM_SEGMENT_ADDRESS(WARMBOOT_RAM_SEGMENT_ID_TZRAM));
     clear_priv_smc_in_progress();
-    /* TODO. */
+    
+    /* Flush cache. */
+    flush_dcache_all();
+    
+    /* Encrypt and save TZRAM into DRAM using a random aes-256 key. */
+    se_generate_random_key(KEYSLOT_SWITCH_LP0TZRAMKEY, KEYSLOT_SWITCH_RNGKEY);
+    
+    flush_dcache_range(tzram_encryption_dst, tzram_encryption_dst + LP0_TZRAM_SAVE_SIZE);
+    flush_dcache_range(tzram_encryption_src, tzram_encryption_src + LP0_TZRAM_SAVE_SIZE);
+    
+    /* Use the all-zero cmac buffer as an IV. */
+    se_aes_256_cbc_encrypt(KEYSLOT_SWITCH_LP0TZRAMKEY, tzram_encryption_dst, LP0_TZRAM_SAVE_SIZE, tzram_encryption_src, LP0_TZRAM_SAVE_SIZE, tzram_cmac);
+    flush_dcache_range(tzram_encryption_dst, tzram_encryption_dst + LP0_TZRAM_SAVE_SIZE);
+    
+    /* Copy encrypted TZRAM from IRAM to DRAM. */
+    memcpy(tzram_store_address, tzram_encryption_dst, LP0_TZRAM_SAVE_SIZE);
+    flush_dcache_range(tzram_store_address, tzram_store_address + LP0_TZRAM_SAVE_SIZE);
+    
+    /* Compute CMAC. */
+    se_compute_aes_256_cmac(KEYSLOT_SWITCH_LP0TZRAMKEY, tzram_cmac, sizeof(tzram_cmac), tzram_encryption_dst, LP0_TZRAM_SAVE_SIZE);
+    
+    /* Write CMAC, lock registers. */
+    APBDEV_PMC_SECURE_SCRATCH112_0 = tzram_cmac[0];
+    APBDEV_PMC_SECURE_SCRATCH113_0 = tzram_cmac[1];
+    APBDEV_PMC_SECURE_SCRATCH114_0 = tzram_cmac[2];
+    APBDEV_PMC_SECURE_SCRATCH115_0 = tzram_cmac[3];
+    APBDEV_PMC_SEC_DISABLE8_0 = 0x550000;
+    
+    /* Save security engine state. */
+    uint8_t *se_state_dst = (uint8_t *)(WARMBOOT_GET_RAM_SEGMENT_ADDRESS(WARMBOOT_RAM_SEGMENT_ID_SE_STATE));
+    se_check_error_status_reg();
+    se_set_in_context_save_mode(true);
+    se_save_context(KEYSLOT_SWITCH_SRKKEY, KEYSLOT_SWITCH_RNGKEY, se_state_dst);
+    flush_dcache_range(se_state_dst, se_state_dst + 0x840);
+    APBDEV_PMC_SCRATCH43_0 = (uint32_t)(WARMBOOT_GET_RAM_SEGMENT_PA(WARMBOOT_RAM_SEGMENT_ID_SE_STATE));
+    se_set_in_context_save_mode(false);
+    se_check_error_status_reg();
+    
+    if (!configitem_is_retail()) {
+        /* TODO: uart_log("OYASUMI"); */
+    }
+    
+    finalize_powerdown();
 }
 
 uint32_t cpu_suspend(uint64_t power_state, uint64_t entrypoint, uint64_t argument) {
diff --git a/exosphere/src/lp0.h b/exosphere/src/lp0.h
index dd5e06468..5b44c804e 100644
--- a/exosphere/src/lp0.h
+++ b/exosphere/src/lp0.h
@@ -5,6 +5,8 @@
 
 /* Exosphere Deep Sleep Entry implementation. */
 
+#define LP0_TZRAM_SAVE_SIZE 0xE000
+
 uint32_t cpu_suspend(uint64_t power_state, uint64_t entrypoint, uint64_t argument);
 
 #endif
\ No newline at end of file
diff --git a/exosphere/src/memory_map.h b/exosphere/src/memory_map.h
index 45d1c27e4..edf26c8c4 100644
--- a/exosphere/src/memory_map.h
+++ b/exosphere/src/memory_map.h
@@ -81,7 +81,7 @@
 #define MMIO_DEVID_EXCEPTION_VECTORS    17
 #define MMIO_DEVID_MAX                  18
 
-#define LP0_ENTRY_RAM_SEGMENT_ID_DECRYPTED_TZRAM    0
+#define LP0_ENTRY_RAM_SEGMENT_ID_ENCRYPTED_TZRAM    0
 #define LP0_ENTRY_RAM_SEGMENT_ID_LP0_ENTRY_CODE     1
 #define LP0_ENTRY_RAM_SEGMENT_ID_CURRENT_TZRAM      2
 #define LP0_ENTRY_RAM_SEGMENT_ID_MAX                3
diff --git a/exosphere/src/pmc.h b/exosphere/src/pmc.h
index 946447647..6c1d78399 100644
--- a/exosphere/src/pmc.h
+++ b/exosphere/src/pmc.h
@@ -23,4 +23,12 @@ static inline uintptr_t get_pmc_base(void) {
 #define APBDEV_PMC_WAKE2_STATUS_0 (*((volatile uint32_t *)(PMC_BASE + 0x168)))
 #define APBDEV_PMC_CNTRL2_0 (*((volatile uint32_t *)(PMC_BASE + 0x440)))
 
+#define APBDEV_PMC_SCRATCH43_0 (*((volatile uint32_t *)(PMC_BASE + 0x22C)))
+#define APBDEV_PMC_SEC_DISABLE8_0 (*((volatile uint32_t *)(PMC_BASE + 0x5C0)))
+#define APBDEV_PMC_SECURE_SCRATCH112_0 (*((volatile uint32_t *)(PMC_BASE + 0xB18)))
+#define APBDEV_PMC_SECURE_SCRATCH113_0 (*((volatile uint32_t *)(PMC_BASE + 0xB1C)))
+#define APBDEV_PMC_SECURE_SCRATCH114_0 (*((volatile uint32_t *)(PMC_BASE + 0xB20)))
+#define APBDEV_PMC_SECURE_SCRATCH115_0 (*((volatile uint32_t *)(PMC_BASE + 0xB24)))
+
+
 #endif
diff --git a/exosphere/src/se.c b/exosphere/src/se.c
index c0587b384..e9dc879b0 100644
--- a/exosphere/src/se.c
+++ b/exosphere/src/se.c
@@ -49,6 +49,11 @@ void se_operation_completed(void) {
     }
 }
 
+void se_check_error_status_reg(void) {
+    if (SECURITY_ENGINE->ERR_STATUS_REG) {
+        generic_panic();
+    }
+}
 
 void se_check_for_error(void) {
     if (SECURITY_ENGINE->INT_STATUS_REG & 0x10000 || SECURITY_ENGINE->FLAGS_REG & 3 || SECURITY_ENGINE->ERR_STATUS_REG) {
@@ -528,6 +533,10 @@ void se_compute_aes_256_cmac(unsigned int keyslot, void *cmac, size_t cmac_size,
     se_compute_aes_cmac(keyslot, cmac, cmac_size, data, data_size, 0x202);
 }
 
+void se_aes_256_cbc_encrypt(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size, const void *iv) {
+    /* TODO */
+}
+
 /* SHA256 Implementation. */
 void se_calculate_sha256(void *dst, const void *src, size_t src_size) {
     /* Setup config for SHA256, size = BITS(src_size) */
@@ -590,3 +599,17 @@ void se_generate_random(unsigned int keyslot, void *dst, size_t size) {
     }
 
 }
+
+
+/* SE context save API. */
+void se_set_in_context_save_mode(bool is_context_save_mode) {
+    /* TODO */
+}
+
+void se_generate_random_key(unsigned int dst_keyslot, unsigned int rng_keyslot) {
+    /* TODO */
+}
+
+void se_save_context(unsigned int srk_keyslot, unsigned int rng_keyslot, void *dst) {
+    /* TODO */
+}
diff --git a/exosphere/src/se.h b/exosphere/src/se.h
index 5a2db189e..22def5126 100644
--- a/exosphere/src/se.h
+++ b/exosphere/src/se.h
@@ -1,6 +1,7 @@
 #ifndef EXOSPHERE_SE_H
 #define EXOSPHERE_SE_H
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <stddef.h>
 
@@ -8,6 +9,8 @@
 
 /* Exosphere driver for the Tegra X1 security engine. */
 
+#define KEYSLOT_SWITCH_LP0TZRAMKEY 0x2
+#define KEYSLOT_SWITCH_SRKKEY 0x8
 #define KEYSLOT_SWITCH_PACKAGE2KEY 0x8
 #define KEYSLOT_SWITCH_TEMPKEY 0x9
 #define KEYSLOT_SWITCH_SESSIONKEY 0xA
@@ -146,6 +149,7 @@ static inline volatile security_engine_t *get_security_engine(void) {
 /* This function MUST be registered to fire on the appropriate interrupt. */
 void se_operation_completed(void);
 
+void se_check_error_status_reg(void);
 void se_check_for_error(void);
 void se_trigger_interrupt(void);
 void se_clear_interrupts(void); /* TODO */
@@ -176,6 +180,7 @@ void se_aes_128_ecb_encrypt_block(unsigned int keyslot, void *dst, size_t dst_si
 void se_aes_256_ecb_encrypt_block(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size);
 void se_aes_ctr_crypt(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size, const void *ctr, size_t ctr_size);
 void se_aes_ecb_decrypt_block(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size);
+void se_aes_256_cbc_encrypt(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size, const void *iv);
 
 /* Hash API */
 void se_calculate_sha256(void *dst, const void *src, size_t src_size);
@@ -189,6 +194,9 @@ void se_synchronous_exp_mod(unsigned int keyslot, void *dst, size_t dst_size, co
 void se_initialize_rng(unsigned int keyslot);
 void se_generate_random(unsigned int keyslot, void *dst, size_t size);
 
-/* TODO: SE context save API. */
+/* SE context save API. */
+void se_set_in_context_save_mode(bool is_context_save_mode);
+void se_generate_random_key(unsigned int dst_keyslot, unsigned int rng_keyslot);
+void se_save_context(unsigned int srk_keyslot, unsigned int rng_keyslot, void *dst);
 
 #endif /* EXOSPHERE_SE_H */